Boltzmann Brains, consciousness and the arrow of time
say that brains during this reverse phase are conscious. I lean towards the first interpretation, for the following reason. If consciousness really was able to somehow distinguish the forward from reverse phases in a Boltzmann fluctuation, it would be quite remarkable. Given that the fundamental laws of physics are time symmetric, nothing should be able to do that, to deduce a true "implicit" arrow of time that goes beyond the superficial arrow of time caused by entropy differences. The whole point of time symmetry, the very definition, is that there should be no such implicit arrow of time. This suggestion would seem to give consciousness a power that it should not have, allow it to do something that is impossible. And if the first interpretation is correct, it seems to call into question the very nature of causality, and its posible role in consciousness. If we are forced to attribute consciousness to sequences of events which occur purely by luck, then causality can't play a significant role. This is the rather surprising conclusion which I reached from these musings on Boltzmann Brains. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-l...@googlegroups.com To unsubscribe from this group, send email to everything-list+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Conscious States vs. Conscious Computations
Jason writes: > A given piece of data can represent an infinite number of different > things depending on the software that interprets it. What may be an > mp3 file to one program may look like snow to an image editor. I'm doubtful that you could find a string of any significant length which both sounds like sensible music and looks like a realistic picture. I'm even more doubtful that the enormous length of the data that would represent the brain activity associated with an observer-moment could be meaningfully interpreted as anything else. My guess is that sufficiently long, meaningful data strings have their meaning implicitly within themselves, because there is no reasonable-length program that can interpret them as anything else. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: against UD+ASSA, part 1
Wei Dai writes: > I promised to summarize why I moved away from the philosophical position > that Hal Finney calls UD+ASSA. Here's part 1, where I argue against ASSA. > Part 2 will cover UD. > > Consider the following thought experiment. Suppose your brain has been > destructively scanned and uploaded into a computer by a mad scientist. Thus > you find yourself imprisoned in a computer simulation. The mad scientist > tells you that you have no hope of escaping, but he will financially support > your survivors (spouse and children) if you win a certain game, which works > as follows. He will throw a fair 10-sided die with sides labeled 0 to 9. You > are to guess whether the die landed with the 0 side up or not. But here's a > twist, if it does land with "0" up, he'll immediately make 90 duplicate > copies of you before you get a chance to answer, and the copies will all run > in parallel. All of the simulations are identical and deterministic, so all > 91 copies (as well as the 9 copies in the other universes) must give the > same answer. This is an interesting experiment, but I have two comments. First, you could tighten the dilemma by having the mad scientist flip a biased coin with say a 70% chance of coming up heads, but then he duplicates you if it comes up tails. Now you have it that the different styles of reasoning lead to opposite actions, while in the original you might as well pick 0 in any case. Second, why the proviso that the simulations are identical and deterministic? Doesn't the reasoning (and dilemma) go through just as strongly if they are allowed to diverge? You will still be faced with a conflict where one kind of reasoning says you have your 91% subjective probability of it coming up a certain way, while logic would seem to suggest you should pick the other one. But, in the case where your instances diverge, isn't the subjective- probability argument very convincing? In particular if we let you run for a while after the duplication - minutes, hours or days - there might be quite a bit of divergence. If you have 91 different people in one case versus 1 in the other, isn't it plausible - in fact, compelling - to think that you are in the larger group? And again, even so, wouldn't you still want to make your choice on the basis of ignoring this subjective probability, and pick the one that maximizes the chances for your survivors: as you say, the measure of the outcomes that you care about? If so, then this suggests that the thought experiment is flawed because even in a situation where most people would agree that subjective perception is strongly skewed, they would still make a choice ignoring that fact. And therefore its conclusions would not necessarily apply either when dealing with the simpler case of a deterministic and synchronous duplication. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: The physical world is real
Youness Ayaita writes: > It's a very trivial fact though that the two approaches are not > equivalent. Nonetheless it's interesting to note it. I argue that we > have good reasons to discard the second approach. The fundamental role > will be assigned to the physical worlds (hence the title of this > message). The difference between the two approaches leads to different > expections to the question "What will I experience next?". > Consequently it can be measured empirically. We find this result by > observing that different physical worlds may produce the same observer > moment (e.g. if the physical worlds differ in a detail not perceivable > by the observer). This assigns a higher probability to the observer > moment when chosen randomly in order to answer the question (it's > multiply counted because it appears more than once in the everyting > ensemble). Opposed to this, every observer moment (in the RSSA within > a given reference class) would have an equal probability to be > selected if we used the second approach. I don't see why taking OMs as primary implies that they would all have equal probability. If two physical worlds instantiate the same OM, that may cause the OM to have higher measure. In the UDASSA model that I prefer, OM measure is essentially the sum of the measures of all programs that output that OM. If two universes instantiate it, both contribute measure to it (as do "Boltzmann brains", demons with boxes, Matrixes and other simulators, etc.). Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
New Scientist: Parallel universes make quantum sense
New Scientist has an article on parallel universes: > David Deutsch at the University of Oxford and colleagues have shown > that key equations of quantum mechanics arise from the mathematics of > parallel universes. "This work will go down as one of the most important > developments in the history of science," says Andy Albrecht, a physicist > at the University of California at Davis. In one parallel universe, > at least, it will - whether it does in our one remains to be seen. It is behind a paywall at http://space.newscientist.com/article/mg19526223.700-parallel-universes-make-quantum-sense.html but I found a copy on Google Groups: http://groups.google.com/group/alt.kq.p/browse_thread/thread/9631b2e37ba5e7a2/fb3202c9c5b71228?lnk=st&q=%22new+scientist%22+deutsch+albrecht&rnum=1#fb3202c9c5b71228 It has a great quote from Tegmark: "The critique of many worlds is shifting from 'it makes no sense and I hate it' to simply 'I hate it'." The thrust of the article is about recent work to fix the two perceived problems in the MWI: non-uniqueness of basis (the universe splits in all different ways) and recovering the Born rule. The basis problem is now considered (by supporters) to be resolved via improved understanding of decoherence. This work (which was not particularly focused on the MWI) generally seems to lead to a unique basis for measurement-like interactions, hence there is no ambiguity in terms of which way the universe splits. As for the Born rule, the article points to the effort begun by Deutsch in 1999 to base things on decision theory. The idea is that we fundamentally care about probability insofar as it influences the decisions and choices we make, so if we can recover a sensible decision theory in the MWI, we have basically explained probability. I've seen a number of critiques of Deutsch's paper but according to this article, subsequent work by David Wallace and Simon Saunders has extended it to the point where things are pretty solid. Hence the two traditional objections to the MWI are now at least arguably dealt with, and given its advantage in terms of formal simplicity (fewer axioms), supporters argue that it should be considered the leading model for QM. This is where we get claims about it being among the most important discoveries in the history of mankind, etc. It's interesting to see the resistance of the physics community to multiverse concepts. It all comes back to the tradition of experimental verification I suppose, which is still pretty much impossible. Really it is more a question of philosophy than of physics as we currently understand these disciplines. We see the same thing happening all over again in string theory. I don't know if you guys are following this at all. String theory is going through a crisis as it has turned out in the past few years that it does not predict a single universe, rather a multiverse where there is a "landscape" of possible sets of parameters, each of which would correspond to a universe. The big problem is that there is no natural or accepted measure (unlike with QM where everyone knew all along that the measure had to be the Born rule and it was just a matter of how many hoops you had to jump through to pull it out of your model). As a result it looks like it might be impossible to get even probabilistic predictions out of the string theory landscape. AFAIK no one within the community has followed our path and looked at algorithmic complexity as a source of measure (i.e. the Universal Distribution, which says that the simplest theories have higher measure). Granted, even if that direction were pursued it would probably be computationally intractable so they still would not be able to pull much out in the way of predictions. Neverthless physicists are skilled at the use of approximation and assumptions to get plausible predictions out of even rather opaque mathematics so it's possible they might get somewhere. But at this point it looks like the resistance is too strong. Rather than string theory making the multiverse respectable as we might hope, it seems likely that the multiverse will kill string theory. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: One solution to the Measure Problem: UTM outputs a qualia, not a universe
Stathis Papaioannou writes: > On 20/09/2007, "Hal Finney" <[EMAIL PROTECTED]> wrote: > > > The lifetime formulation also captures the intuition many people have > > that consciousness should not "jump around" as observer moments are > > created in the various simulations and scenarios we imagine in our > > thought experiments. That was the conclusion I reached in the posting > > referenced above, that teleportation might in some sense "not work" > > even though someone walks out of the machine thousands of miles away > > who remembers walking into it. The measure of such a lifetime would be > > substantially less than that of a similar person who never teleports. > > I have great conceptual difficulty with this idea. It seems to allow > that I could have died five minutes ago even though I still feel that > I am alive now. (This is OK with me because I think the best way to > look at ordinary life is as a series of transiently existing OM's > which create an illusion of a self persisting through time, but I > don't think this is what you were referring to.) You will probably agree that there are some branches of the multiverse where you did indeed die five minutes ago, and perhaps people are standing around staring in shock at your dead body. And supposing that you had just had a narrow escape from a perilous situation, you might even consider that those branches where you died are of greater measure than those where you survived. That's basically all my analysis says, as far as normal life. The main novelty is what it has to say about exotic thought experiments like teleportation and resurrection. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: One solution to the Measure Problem: UTM outputs a qualia, not a universe
[By the way, I notice that I do not receive my own postings back in email, which makes my archive incomplete. Does anyone know if there is a way to configure the mailing list reflector to give me back my own messages?] Russell Standish wrote: > On Wed, Sep 19, 2007 at 12:10:33PM -0700, "Hal Finney" wrote: > > The lifetime formulation also captures the intuition many people have > > that consciousness should not "jump around" as observer moments are > > created in the various simulations and scenarios we imagine in our > > thought experiments. That was the conclusion I reached in the posting > > referenced above, that teleportation might in some sense "not work" > > even though someone walks out of the machine thousands of miles away > > who remembers walking into it. The measure of such a lifetime would be > > substantially less than that of a similar person who never teleports. > > > > Hal Finney > > I note that you have identified yourself with the the ASSA camp in the > past (at least I say so in my book, so it must be true, right! :). What > you are proposing above is an anti-functionalist position. The question is > does functionalism necessarily imply RSSA, and antifunctionalism imply > the ASSA? ie, does this whole RSSA/ASSA debate turn on the question of > functionalism? The distinction I am drawing seems somewhat orthogonal to the RSSA/ASSA debate. Suppose someone is about to die in a terrible accident. From the 1st person perspective, RSSA would say that he expects to survive through miraculous good luck. ASSA would say that he expects to die and never experience anything again. Now suppose that in most universes an advanced, benevolent human/AI civilization later recreates his mental state and in effect resurrects him in a sort of heaven. Both ASSA and RSSA might now say that his expectation prior to the accident should be to wake up in this "heaven", that that is his most likely "next" experience. My argument suggests otherwise, that the chance of this being his next experience would be rather low. However it basically leaves the RSSA/ASSA distinction intact. We would go back to the situation where RSSA predicts a miraculously lucky survival of the accident while ASSA predicts death. But actually my analysis is supportive of the ASSA in this form, in that the measure of a lifetime which ends in the accident is much higher than the measure of one which survives. As far as functionalism, I agree that this kind of analysis argues against it. Indeed the post from Wei Dai which introduced this concept, which I quote here, http://www.udassa.com/origins.html (apologies for the incompleteness of this web site), suggests that the size of a computer would affect measure, contradicting functionalism. Frankly I suspect that Bruno's analysis would or should lead to the same kind of conclusion. I wonder if he supports strict functionalism? Would he say "yes doctor" to any and all "functional" brain replacements? Or would some additional investigation be appropriate? > I wonder where this leaves Mallah, who admits to computationalism, yet > is died-in-the-wool ASSA? Indeed I have often wondered where in the world is Jacques Mallah, who was so influential on this list in the past but who seems to have vanished utterly from the net. Actually, I wrote that sentence based on previous Google searches, but just now I discovered that as of two weeks ago he has published his first communication in many years: http://arxiv.org/abs/0709.0544 . Here is his abstract, which seems similar in its goals to your own work: : The Many Computations Interpretation (MCI) of Quantum Mechanics : Authors: Jacques Mallah : (Submitted on 4 Sep 2007) : : Abstract: Computationalism provides a framework for understanding : how a mathematically describable physical world could give rise to : conscious observations without the need for dualism. A criterion : is proposed for the implementation of computations by physical : systems, which has been a problem for computationalism. Together : with an independence criterion for implementations this would allow, : in principle, prediction of probabilities for various observations : based on counting implementations. Applied to quantum mechanics, : this results in a Many Computations Interpretation (MCI), which is : an explicit form of the Everett style Many Worlds Interpretation : (MWI). Derivation of the Born Rule emerges as the central problem for : most realist interpretations of quantum mechanics. If the Born Rule : is derived based on computationalism and the wavefunction it would : provide strong support for the MWI; but if the Born Rule is shown not : to follow from these to an experimentally falsifi
Re: One solution to the Measure Problem: UTM outputs a qualia, not a universe
[I want to first note for the benefit of readers that I am Hal Finney and no relation to Hal Ruhl - it can be confusing having two Hal's on the list!] Rolf Nelson writes: > UDASSA (if I'm interpreting it right, Hal?) says: > > 1. The measure of programs that produce OM ("I am experiencing A, and > I remember my previous experience as B") as its single output, > compared to the measure of programs that produce OM ("I am not > experiencing A, and I remember my previous experience as B") as its > single output, is what we perceive as "the likelihood of A following > B, rather than A not following B." I think you mean, "the likelihood of A following B rather than not-A following B". That's probably reasonable, although I suggested a somewhat different approach in this (as usual) somewhat overly long posting: http://www.nabble.com/Teleportation-thought-experiment-and-UD%2BASSA-tf3057020.html#a8498222 Imagine that we could write down a description of a person's mental states for his whole lifetime, from birth to death. Every possible such sequence would be a possible lifetime and would exist in the universe of all information patterns. Some would have higher measure than others. As usual, it is plausible that the highest-measure such lifetimes would be those which exist as parts of universes that have reasonably simple descriptions. Then we can get at your question of what is the likelihood of A following B by asking, what is the measure of all lifetimes which experience event B followed by event A, compared to the measure of all lifetimes which experience event B not followed by event A. The difference from what you expressed would be, for example, if some future civilization creates simulated OMs which remember B followed by A, while in the "real world" B did not get followed by A. Your OM based formulation might have those future OMs add quite a bit of measure to B-then-A, while the lifetime based formulation would consider those as less important, because of the discontinuity between the "original" lifetime and the future simulation of B-then-A. The lifetime formulation also captures the intuition many people have that consciousness should not "jump around" as observer moments are created in the various simulations and scenarios we imagine in our thought experiments. That was the conclusion I reached in the posting referenced above, that teleportation might in some sense "not work" even though someone walks out of the machine thousands of miles away who remembers walking into it. The measure of such a lifetime would be substantially less than that of a similar person who never teleports. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: One solution to the Measure Problem: UTM outputs a qualia, not a universe
Rolf writes: > World-Index-Compression Postulate: The most probable way for the > output of a random UTM program to be a single qualia, is through > having a part of the program calculate a Universe, U, that is similar > to the universe we currently are observing; and then having another > part of the program search through the universe and pick out a > substring by using an search algorithm SA(U) that tries to find a > random sentient being in U and emit his qualia as the final output. Yes, as you note later this is very similar to the concept I called UD+ASSA or just UDASSA and described in a series of postings to this list back in 2005. It was not original with me but actually was based on an idea of Wei Dai, who founded this last way back in 1998. I was working at one point on the udassa.com site to bring the ideas together but never finished it. I'm surprised that guy found it, I don't recall mentioning that URL. Must have let it slip sometime! You might enjoy this old post where I tried to work out in some plausible detail the size of a program to output a mental state, or as you say a quale, and came up with an answer in the 10s of kilobits, not far from your estimate. http://www.nabble.com/UDist-and-measure-of-observers-tf3056759.html Hal --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: How would a computer know if it were conscious?
Part of what I wanted to get at in my thought experiment is the bafflement and confusion an AI should feel when exposed to human ideas about consciousness. Various people here have proffered their own ideas, and we might assume that the AI would read these suggestions, along with many other ideas that contradict the ones offered here. It seems hard to escape the conclusion that the only logical response is for the AI to figuratively throw up its hands and say that it is impossible to know if it is conscious, because even humans cannot agree on what consciousness is. In particular I don't think an AI could be expected to claim that it knows that it is conscious, that consciousness is a deep and intrinsic part of itself, that whatever else it might be mistaken about it could not be mistaken about being conscious. I don't see any logical way it could reach this conclusion by studying the corpus of writings on the topic. If anyone disagrees, I'd like to hear how it could happen. And the corollary to this is that perhaps humans also cannot legitimately make such claims, since logically their position is not so different from that of the AI. In that case the seemingly axiomatic question of whether we are conscious may after all be something that we could be mistaken about. Hal --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
How would a computer know if it were conscious?
Various projects exist today aiming at building a true Artificial Intelligence. Sometimes these researchers use the term AGI, Artificial General Intelligence, to distinguish their projects from mainstream AI which tends to focus on specific tasks. A conference on such projects will be held next year, agi-08.org. Suppose one of these projects achieves one of the milestone goals of such efforts; their AI becomes able to educate itself by reading books and reference material, rather than having to have facts put in by the developers. Perhaps it requires some help with this, and various questions and ambiguities need to be answered by humans, but still this is a huge advancement as the AI can now in principle learn almost any field. Keep in mind that this AI is far from passing the Turing test; it is able to absorb and digest material and then answer questions or perhaps even engage in a dialog about it. But its complexity is, we will suppose, substantially less than the human brain. Now at some point the AI reads about the philosophy of mind, and the question is put to it: are you conscious? How might an AI program go about answering a question like this? What kind of reasoning would be applicable? In principle, how would you expect a well-designed AI to decide if it is conscious? And then, how or why is the reasoning different if a human rather than an AI is answering them? Clearly the AI has to start with the definition. It needs to know what consciousness is, what the word means, in order to decide if it applies. Unfortunately such definitions usually amount to either a list of synonyms for consciousness, or use the common human biological heritage as a reference. From the Wikipedia: "Consciousness is a quality of the mind generally regarded to comprise qualities such as subjectivity, self-awareness, sentience, sapience, and the ability to perceive the relationship between oneself and one's environment." Here we have four synonyms and one relational description which would arguably apply to any computer system that has environmental sensors, unless "perceive" is also merely another synonym for conscious perception. It looks to me like AIs, even ones much more sophisticated than I am describing here, are going to have a hard time deciding whether they are conscious in the human sense. Since humans seem essentially unable to describe consciousness in any reasonable operational terms, there doesn't seem any acceptable way for an AI to decide whether the word applies to itself. And given this failure, it calls into question the ease with which humans assert that they are conscious. How do we really know that we are conscious? For example, how do we know that what we call consciousness is what everyone else calls consciousness? I am worried that many people believe they are conscious simply because as children, they were told they were conscious. They were told that consciousness is the difference between being awake and being asleep, and assume on that basis that when they are awake they are conscious. Then all those other synonyms are treated the same way. Yet most humans would not admit to any doubt that they are conscious. For such a slippery and seemingly undefinable concept, it seems odd that people are so sure of it. Why, then, can't an AI achieve a similar degree of certainty? Do you think a properly programmed AI would ever say, yes, I am conscious, because I have subjectivity, self-awareness, sentience, sapience, etc., and I know this because it is just inherent in my artificial brain? Presumably we could program the AI to say this, and to believe it (in whatever sense that word applies), but is it something an AI could logically conclude? Hal --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Boltzmann brains
Stathis Papaioannou <[EMAIL PROTECTED]> writes: > On 01/06/07, "Hal Finney" <[EMAIL PROTECTED]> wrote: > > The reference to Susskind is a paper we discussed here back > > in Aug 2002, Disturbing Implications of a Cosmological Constant, > > http://arxiv.org/abs/hep-th/0208013 . The authors argued that in current > > cosmological models the universe dies a heat death and falls into a steady > > state of exponential expansion which goes on forever. In that state, > > quantum gravity fluctuations will eventually cause macroscopic objects > > to appear. This is extremely rare but still with infinite time to work > > with, every object will appear an infinite number of times. That includes > > disembodied brains, the so-called Boltzmann brains, as well as planets and > > whole universes. But the smaller objects are vastly more common, hence it > > is most likely that our experiences are due to us being a Boltzmann brain. > > It isn't generally the case that given a non-zero probability of an event E > occurring per trial (or per unit time period), then as the number of trials > n approaches infinity the probability of E occurring approaches 1. For > example, if Pr(E) = 1/2^n, then even though Pr(E) is always non-zero, the > probability of ~E as n->inf is given by the infinite product of (1-1/2^n), > which converges to approximately 0.288788, not zero. So if the exponential > expansion is associated with a continuous decrease in the probability that > an event of interest will occur during a unit time period, that event may > still never occur given infinite time, even though at no point can the event > be said to be impossible. Right, but apparently the physics doesn't work this way. The papers just seem to take the size of the necessary object in Planck units and say the probability of it popping into existence is 1/e^size. This is constant and therefore it will happen an infinite number of times. > > This has a few bad implications; one is that our perceptions should end > > and not continue (but they do continue) and another is that brains would > > be just as likely to (falsely) remember chaotic universes as lawful ones > > (but we only remember lawful ones). So this model is not considered > > consistent with our experiences. > > Another possibility is that Boltzmann Brains arising out of chaos are the > observer moments which associate to produce the first person appearance of > continuity of consciousness and an orderly universe. Binding together > observer moments thus generated is no more difficult than binding together > observer moments generated in other multiverse theories. So how would this explain why we see an orderly universe? I think we would have to say that Boltzmann brains that remember an orderly universe are substantially smaller (take up fewer Planck units) than those that remember chaotic ones. I considered this possibility but I couldn't come up with a good justification. Now, keep in mind that the Boltzmann brain does not have to literally be a brain, with lobes and neurotransmitters and blood; it could be any equivalent computational system. Chances are that true "Boltzmann brains" would be small solid-state computers that happen to hold programs that are conscious. Shrinking the brain even a little increases its probability of existence tremendously. (I am assuming that probability makes sense even though we are speaking of events that happen a countably infinite number of times; both Boltzmann brains and whole universes like ours will appear infinitely often in the de Sitter state, but the smaller systems will be far more frequent. I assume that this means that we would be more likely to experience being the small systems then the big ones, even though both happen an infinite number of times.) So to explain the lawfulness we would have to argue that Boltzmann brains that remember lawful universes can be designed to be smaller than those that remember chaotic universes, as well as slightly lawless flying-rabbit universes. It's not completely implausible that the greater simplicity of a lawful universe would allow the memory store of the Boltzmann brain to be made smaller, as it would allow clever coding techniques to compress the data. However one would think that memories of universes even simpler than our own would then be that much more likely, as would memories of shorter lifetimes and other possibilities to simplify and shrink the device. This explanation doesn't really seem to work. Hal --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: Boltzmann brains
ve a lesser share of the universe's total measure. Also, the amount of information to specify the location of such a brain in terms of Planck moments since the Big Bang would be vastly greater than for brains like ours existing in the relative youth of the universe. A measure concept related to information might therefore reduce the measure of such brains to insignificance. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~--~~~~--~~--~--~---
Re: computationalism and supervenience
Russell Standish writes: > Why do you say this? Surely physical supervenience is simply > supervenience on some physical object. Physical objects are spread > across the multiverse, and are capable of reacting to all > counterfactuals presented to it. > > Inside views are local - but the whole shebang must be spread across > the Multiverse. I suppose it depends on your definitions. As I suggested, supervenience in a single world model means that consciousness depends on local physical activity, and not on causally unconnected events. In a multiverse, actions in parallel worlds are causally unconnected to actions here. It seems rather odd to say that the supervenience thesis says that whether my computer is conscious depends on what is happening in some remote parallel universe. I also think there are problems with this notion that objects are spread across the multiverse, and in particular that all counterfactuals are tested. It's not clear to me that we can unambiguously define the counterpart to this particular object in an arbitrary multiverse. For very "near" or "similar" multiverses it may seem unproblematic, while for extremely "far" or "different" multiverses there will obviously be no counterparts. There would probably be a gray area in the middle in which an object was related to one in our universe but perhaps not exactly the same. This exposes a difficulty with the notion that all counterfactuals are tested. In the first place, many thought experiments aim to refrain from testing counterfactuals - Maudlin's is of this nature. Something has to go seriously wrong with Maudlin's scenario for counterfactuals to be tested. In the second place, many counterfactuals may be bizarre and unlikely, so that the circumstances under which they are tested may require extremely strange events. These situations would suggest that such counterfactuals will only be tested in relatively remote parts of the multiverse, parts quite different from our own. And then we have to ask, is it really the "same" machine that is being tested? And by "same" here, I think we mean more than just "designed the same" or "isomorphic" - we mean that it has some kind of shared identity, that in some sense this *is* the machine we see in our universe, just exposed to different inputs. Given the problems I mentioned with this notion of identity across the multiverse, it's not clear that this concept makes sense. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: computationalism and supervenience
Russel Standish writes: > Or my point that in a Multiverse, counterfactuals are instantiated > anyway. Physical supervenience and computationalism are not > incompatible in a multiverse, where "physical" means the observed > properties of things like electrons and so on. I'd think that in the context of a multiverse, physical supervenience would say that whether consciousness is instantiated would depend only on physical conditions here, at this point in the multiverse, and would not depend on conditions elsewhere. It would be a sort of "locality condition" for the multiverse. In that case it seems you still have a problem because even if counterfactuals are tested elsewhere in the multiverse, whether they are handled correctly will not be visible locally. So you'd still have a contradiction, with supervenience saying that consciousness depends only on local physical conditions, while computationalism would say that consciousness depends on the results of counterfactual tests done in other branches or worlds of the multiverse. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: computationalism and supervenience
I am sorry that I have not been able to keep up with the list lately. I can only peek in occasionally. My interpretation of the question of computationalism vs supervenience can be put succinctly. Computationalism says that consciousness depends both on actual behavior and on counterfactuals. Therefore, it depends both on what happens and on what doesn't happen. Supervenience says that consciousness depends only on physical behavior; hence it depends only on what happens. Since computationalism says that consciousness depends on what doesn't happen, while supervenience says that it depends only on what happens, the two doctrines are inconsistent. To marry them would require altering computationalism so that it no longer depended on counterfactuals, which then requires us to say that all systems implement all calculations. As far as this latter question, the framework I adopted and adapted from Wei Dai, which I call UD+ASSA, suggests that there is a sense in which it is true, but it is not significant or meaningful. The UDASSA framework seeks to calculate the measure of a conscious experience. We start by thinking of a conscious experience as something that can be described as an abstract information pattern. Any physical system which instantiates that information pattern can be said to contribute to the measure of that conscious experience. The Universal Distribution defines the measure of an information pattern as the fraction of all programs that output that pattern. Equivalently, the measure is the sum of 1/2^L_n, where L_n is the length in bits of the nth program that outputs the pattern. Short programs have higher measure than long ones; hence to a good approximation the measure depends on the length of the shortest program that outputs it. If we consider all programs, some of them instantiate or simulate "physical" universes. They have their own laws of physics and initial conditions. Some are complex, some simple. In those universes we may find physical systems which we would naively view as instantiating particular computations, even conscious computations. We would like to say that such universes add to the measure of those computations. In the UDASSA framework, this is handled by imagining a two part program. The first part creates and runs the universe; the second part scans the output of the first part and outputs the abstract information pattern that represents the conscious experience. The size of this two part program is the sum of the size of its parts. Only if both parts are small will the contribution to the measure of the experience be large. As has been discussed here, in principle you can find a mapping from any physical system to any computation. This threatens to lead to the conclusion that every consciousness is instantiated by every physical system. Traditionally, computationalism opposed that conclusion by insisting on support for counterfactuals. But the UDASSA framework handles it in a different way. In the UDASSA framework, a mapping from, say, a solid rock to an abstract information pattern representing a moment of human consciousness would be a very large program. In truth, this mapping program wouldn't even need to use the rock. It could output the human information pattern just as easily without the help of information from the rock. The mapping program will need to include all of the information and programming needed to generate the human consciousness information pattern essentially from scratch. That's going to be a very large program. In contrast, a mapping program that goes from a human brain to an abstract information pattern representing a moment of human consciousness can be quite compact. It would use the physical information from the human brain state and translate that to whatever form was used to abstractly specify the computational state. While this might be modestly complex, it would be far, far simpler than the nearly-astronomical complexity needed to output a human brain experience from a rock. The result is that physical systems which have plausible "naive" interpretations as implementing certain computations will contribute significantly to the measure of such computations; while physical systems where we would need a contrived and complex mapping will contribute negligibly to such measure. This provides a reason, within this framework, to neglect the possible existence of conscious entities created by non-conscious computations. Any mapping which could specify such an entity will be enormous and will not contribute meaningfully to the measure of such entities. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROT
Re: Bruno's argument
A useful model of computation is the Turing Machine. A TM has a tape with symbols on it; a head which moves along the tape and which can read and write symbols, and a state machine with a fixed number of states that controls head movement and symbol writing based on the current state and the symbol at the head's current location. It has been shown that this relatively simplistic model is able to do anything that more sophisticated computer models can do. We can consider the "state" of a TM to be made up of the conjunction of three things: the current state of the tape (i.e. the string of symbols written there); the position of the head; and the state of the internal state machine. Maybe it would be best to call this the superstate because normally the "state" of the TM just refers to its internal state machine state. The TM can then be said to advance from superstate to superstate according to its internal rules and the contents of the tape. If a TM ever gets into the same superstate twice, it is in an infinite loop. This is because the TM is fully deterministic and so it will always go into the same successor superstate from a given superstate. Halting TM's never get into the same superstate twice. Therefore halting TM's go through a unique succession of superstates, from the first to the last. We can map or label a TM's superstates with successive integers, corresponding to the order that it goes through the superstates of a computation. In this mapping, the only difference between two different computations is their length. If two computations had the same length N, they would both go through states labeled 0, 1, 2, ..., N. What is a computation? A TM computation has two parts. One is the initial conditions: the initial value on the tape, the initial head position. The other is the set of rules used, the internal state machine that controls the machine. Together these two parts define a trajectory of the TM through a sequence of superstates. We often think of the internal state machine as being like the "program" and the initial contents of tape as being the "data". However, as Turing was the first to recognize, this distinction is not always useful, and sometimes it makes more sense to think of at least part of the tape contents as being program rather than data. In particular, the Universal TM treats part of the tape as a specification for a specific other TM that it will emulate, and the remainder of the tape is then the input to that TM. Generally, when we think of counterfactuals in a TM computation we mean to change the data, not the program. We don't mean to ask, what would happen if you ran a different program on the same data. Rather, we mean, what would happen if you ran the same program on different data. We want to say that two computations are equivalent only if they have the same counterfactual behavior - that is, if the programs would behave the same on all data. One problem with this is noted above, that we cannot always cleanly distinguish program and data. In the case of the UTM, is the prefix part of the tape, that defines the particular TM to emulate, program or data? If it is program, we would not try to vary it in considering whether two computations are equivalent. If it is data, we should consider such variations. In general, I don't think we can always distinguish these cases cleanly. UTMs can be nested to any desired degree. What is program to one is data to another. More complex UTM computations may be aided by certain patterns on the tape which will disrupt the computation if they are changed. Another problem is that a more complex mapping may be able to be set up between two different computations even if we consider counterfactuals as all different initial tape configurations. We could make the mapping be a function of the superstate as defined above. Two computations with different initial tapes will start in different superstates, hence the mapping is still unique. And it will be robust over all possible inputs and hence all possible counterfactual computations. On these considerations, It seems to me that there are problems with basing the distinction between computations on support for counterfactuals. TMs make the very notion of counterfactuals rather fuzzy, and still admit the possibility of mappings between computations that remain robust even in the face of counterfactuals. My preferred view is to focus on the algorithmic complexity of the mapping between two computations, and to ask whether the information needed to specify the mapping is less than the information needed to write down the computation from scratch. If not, if the mapping is substantially bigger than the computation it purports to describe, then the correspondence is an illusion and is not real. Hal Finney --~--~-~--~~~---~--~~ You received this message becaus
Re: Interested in thoughts on this excerpt from Martin Rees
ated in this paper, then most OMs will be far in the future, hence by the ASSA we are unlikely to be experiencing present-day OMs. This was the basic concept of a paper we discussed back in 2002: > Dyson, L., Kleban, M. & Susskind, L. Disturbing implications of a > cosmological constant. Preprint <http://xxx.lanl.gov/abs/hep-th/0208013>, > (2002). They used a slightly different physics model but came up with the same idea, that most OMs should be in the distant future, contradicting what we call the ASSA, which I think they just considered an implication of the anthropic principle. You might be right that these papers could be read as an argument against a single-universe model, if in fact we could come up with a good justification within a multiverse model for decreasing OM measure in the future. We'd probably have to have a pretty strong argument in that regard, though. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Interested in thoughts on this excerpt from Martin Rees
Saibal Mitra writes: > From: ""Hal Finney"" <[EMAIL PROTECTED]> > > The real problem is not just that it is a philosophical speculation, > > it is that it does not lead to any testable physical predictions. > > The string theory landscape, even if finite, is far too large for > > systematic exploration. Our ideas, with an infinite number of possible > > universes, are even worse. > > I'm not so sure that our ideas are worse. I should clarify, I meant that our ideas are even worse in terms of systematic exploration of all the possibilities, because we generally consider an infinity of possible universes, while the string theory landscape predicts (some people say) about 10^500 possible universes. > If you read some recent articles, > e.g.: > > http://arxiv.org/abs/astro-ph/0607227 > > you see that they haven't really formulated rigorous theories about measure, > probabilities etc. of the multiverse. It's still very much in the > "handwaving" stage. This is actually a very interesting paper, by Starkman and Trotta. I had seen some mention of it but hadn't tracked it down. Here is the abstract: "We revisit anthropic arguments purporting to explain the measured value of the cosmological constant. We argue that different ways of assigning probabilities to candidate universes lead to totally different anthropic predictions. As an explicit example, we show that weighting different universes by the total number of possible observations leads to an extremely small probability for observing a value of Lambda equal to or greater than what we now measure. We conclude that anthropic reasoning within the framework of probability as frequency is ill-defined and that it cannot be used to explain the value of Lambda, nor, likely, any other physical parameters." The paper is pretty technical but I thought I could understand the gist of it. The cosmological constant ("Lambda") is a repulsive force which drives galaxies apart in the Big Bang model. Until a few years ago it was thought to be entirely theoretical, but since then observations indicate that it is real, and that the universal expansion is accelerating. The question then becomes what would happen in universes with different values of the CC. The paper basically shows that observers (or civilizations) can last longer in universes with smaller CC's. The CC eventually puts an end to the observations that can be made, because the expansion gets too fast and there is no longer enough energy density. The higher the CC, the sooner this happens. With CC's as high as what we observe, the theoretical lifetime of civilization is much shorter than in universes with smaller CC's. The authors choose to use as their measure, the number of times the CC can be measured in a given universe. This makes low-CC universes have a much higher measure, because the window for CC observations is longer in those. Hence they conclude that the highest probability is for a CC much smaller than we observe, and so our own CC value cannot be explained anthropically. This is in contrast to earlier results which used different measures, such as the number of galaxies, and found that our CC results were consistent with anthropic considerations. The authors argue that their measure is at least as philosphically justifiable as those earlier papers, and their real point is that no measure can be justified as better than another, hence all anthropic reasoning is just hand-waving. In our terms we might put it like this. The new paper essentially uses a measure which is the number of possible observer-moments in the universe. Universes with a high CC go through a "big rip" process eventually, accelerating to a super-expansion mode and presumably putting an end to observers. Universes with a low or zero CC go through this much later or not at all, allowing for more observer-moments. Hence this measure gives a bonus to universes that last a long time. Earlier papers apparently looked at a snapshot of time similar to the present day, and in effect based the measure on the number of observers (assumed to be proportional to the number of galaxies). So we have a distinction between an observer-moment measure and an observer measure. The two apparently give very different results, the OM measure preferring long-lasting universes while the observer measure is more interested in the size of the universe. I guess I'll stop here and see if there is more interest. To leave with a few questions: Is there any fundamental way to decide which measure is "best"? Do the OM measure and the observer measure really give different results, and is that significant? Are there other measures that might be used, and what results would they get? And finally, will this apparent failure of anthropic reasoning discre
Re: Interested in thoughts on this excerpt from Martin Rees
e general approach of physics needs to be substantially rethought. So the bottom line is that Rees leaves us with a highly misleading perspective. While he personally may be happy with anthropic ideas, most physicists are not. Where I live in Santa Barbara, Nobelist David Gross, head of the KITP at UCSB, is famous for his active hostility to the concept. So opposed are physicists to adopting all-universe models that they are ready to abandon twenty years of work and strike off in a new direction rather than face the immensity of the anthropic universe. Now, I'm sure that some physicists will continue to work on these ideas, just as a minority has continued to work on rivals to string theory all these years. The bottom line is that unless some way is found to make specific, testable predictions (and not the kind of hand-waving we sometimes get away with around here, explaining why bunnies can't fly), the anthropic universe is not physics. It is philosophy, and physicists want nothing to do with it. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
RE: Bruno's argument
Apologies for being out of touch with the list, I can only dip a toe in occasionally these days. Stathis wrote: > It seems to me trivially obvious that any sufficiently complex physical > system implements any finite computation, just as any sufficiently > large block of marble contains every marble statue of a given size. > The difference between random noise (or a block of marble) on the one > hand and a well-behaved computer (or the product of a sculptor's work) > on the other is that the information is in the latter case presented > in a way that can interact with the world containing the substrate of > its implementation. But I think that this idea leads to almost the same > conclusion that you reach: it really seems that if any computation can > be mapped to any physical substrate, then that substrate is superfluous > except in that tiny subset of cases involving well-behaved computers that > can handle counterfactuals and thus interact with their environment, > and we may as well say that every computation exists by virtue of its > status as a platonic object. I say "almost" because I can't quite see > how to prove it, even though I suspect that it is so. If we take the next step, though, the real question changes somewhat. Let's imagine that what we see as physical objects are actually the result of some kind of computational process. We are living in a virtual universe. Even if you don't believe it, try following the logic for a minute. In that case, this physical object, this block of marble, is actually a computational process. But if we continue to believe that the complex "physical" system implements every computation, then what we are really saying is that a complex "computational" system implements every computation - because the complex physical system is actually (or at least, hypothetically could be) a manifestation of a computation. So we should really reword Stathis claim. Instead of "any sufficiently complex physical system implements any finite computation", it must be, "any sufficiently complex computation implements any finite computation". And IMO that is a rather more interesting claim, and perhaps more amenable to analysis since it stays within the realm of mathematics and logic, rather than crossing boundaries between the physical and the ideal. Indeed, it is not inherently surprising or implausible that a computation can be said to implement more than one computation. If we think of a computation as a sequence of logical steps A, B, C, ... Z, then it automatically can be said to also implement every subsequence of those steps: for example, "J, K, L" is implemented by that sequence, as is "O, P, Q, R, S, T". It might also be that computation A could be embedded in computation B in a more subtle way. We could, for example, interleave the computations of A and B, doing A's operations on the odd-numbered steps and doing B's operations on the even-numbered ones. With Stathis' "sufficiently complex" computations, we could imagine that the computation is so long and so messy and confusing that, with enough work, we could indeed hope to find virtually any smaller computation embedded within this complexity. On the other hand it clearly won't do to say that every computation implements every other. The identity computation F(x) = x does not implement a master-level chess playing program. So there must be a threshold of complexity before we could start making this kind of claim. This raises the question of whether there is an objective fact about whether computation A implements computation B. And should it count if A merely comes "close" to implementing B? There is a paradox due to Putman which argues that even a counting program "loop: x = x + 1; goto loop;" will implement every program. Going back to my first example of some program that goes through 26 steps or states A through Z, we can identify the initial state of the counting program x=1 with state A; we identify x=2 with state B, and so on up through x=26 which is state Z. So our counting program can be said, in a sense, to implement our A-Z program, if we interpret it the right way. Then there are various responses to this, and counter-arguments as well, which I won't get into. IMO there is a gray area where it is hard to say whether A truly implements B or if the correspondence is in the mind of the beholder. The relevance to our issues is when we start talking about measures over computer programs and computations, and relating them to first-person experiences, it's necessary to consider whether it is meaningful to say what a given computation is doing. If every sufficiently complex computation implements every other, then that contradicts any reasoning based on the differences between different
RE: A calculus of personal identity
Stathis Papaioannou writes: > Hal Finney writes: > > > What I argued was that it would be easier to find the trace of a person's > > thoughts in a universe where he had a physically continuous record than > > where there were discontinuities (easier in the sense that a smaller > > program would suffice). In my framework, this means that the universe > > would contribute more measure to people who had continuous lives than > > people who teleported. Someone whose life ended at the moment of > > teleportation would have a higher measure than someone who survived > > the event. Therefore, I would view teleportation as reducing measure > > similarly to doing something that had a risk of dying. I would try to > > avoid it, unless there were compensating benefits (as indeed might be > > the case, just as people willingly accept the risk of dying by driving > > to work, because of the compensating benefits). > > > > You can say that "by definition" the person survives, but then, you > > can say anything by definition. I guess the question is, what is the > > reasoning behind the definition. > > OK, this is the old ASSA versus RSSA distinction. But leaving this > argument aside, I don't see how teleportation could be analogous to a > risky, measure reducing activity if it seemed to be a reliable process > from a third person perspective. If someone plays Russian Roulette, we > both agree that from a third person perspective, we are likely to observe > a dead body eventually. But with teleportation (destructive, to one place) > there is a 1:1 ratio between pre-experiment subjects and post-experiment > subjects from a third person perspective. Are you suggesting that the > predicted drop in measure will have no third person observable effect? First, I tend to think that the phrase "third person observable" is something of a contradiction. Observation is a first-person activity. I would prefer to think of third person effects as simply the physical record of events. In this case, there will definitely be a third person effect. Having someone teleport is a third-person difference from not having them teleport. We are talking about two cases here that are third-person distinguishable, with very different physical histories, hence it is plausible that there be different subjective first-person effects. As far as the comparison with Russian Roulette, if someone only plays it once, there might not be a third person difference. Yet I would argue his measure was reduced (in the multiverse). Really, when we are talking about third person records, all we have is the actual sequence of events that occurs. Suppose someone plays Russian Roulette multiple times. In this universe, perhaps we see them pull the trigger five times and survive, and on the sixth pull they die. That subjective history, of playing RR six times, is instantiated in this universe. This universe contributes measure to that history. Other universes, not observable to us, may have him die after different trials. Each of those contributes measure to subjective histories that end at different points. The result is that the measure of his lifespan is reduced at each trigger pull, but that in any single third-person universe that reduction in measure is unobservable. Instead we see no change until the final trigger pull. Consider this example: someone commits to killing himself if you die, and now you play Russian Roulette yourself. Each time you pull the trigger you reduce his measure, that of the other person who will kill himself if you die. But you will never observe him dying (in the first-person sense). This is a case of an unobservable measure decrease which you might nevertheless believe in. > > As far as Lee's suggestion that people could be dying thousands of > > times a second, my framework does not allow for arbitrary statements > > like that. Given a physical circumstance, we can calculate what happens. > > It's not just arbitrary what we choose to say about life and death. > > We can calculate the measure of different subjective life experiences, > > based on the physical record. > > > > If we wanted to create a physical record where this framework would > > be compatible with saying that people die often, it would be necessary > > to physically teleport people thousands of times a second. Or perhaps > > the same thing could be done by freezing people for a substantial time, > > reviving them for a thousandth of a second, then re-freezing them again > > for a while, etc. > > > > If we consider the practical implications of such experiments I don't > > think it is so implausible to view them as being worse than living a > > single, conn
RE: A calculus of personal identity
Lee Corbin writes: > Stathis writes > > Hal Finney in his recent thread on teleportation thought > > experiments disagrees with the above view. He suggests > > that it is possible for a subject to apparently undergo > > successful teleportation, in that the individual walking > > out of the receiving station has all the appropriate > > mental and physical attributes in common with the individual > > entering the transmitting station, but in reality not survive > > the procedure. I have difficulty understanding this, as it > > seems to me that the subject has survived by definition. > > Well, if you've characterized his views correctly, then he's > not in agreement with you, me, and Derek Parfit. What might > be fun to explore is how desperate some people would have to > be in order to teleport (or perhaps how lucrative the > opportunity?). Also, I suppose that if you confided to them > that this was happening to them all the time thousands of > times per second, they'd still have some unfathomable reason > not to go near a teleporter. Sorry, I have been reading the list somewhat lightly recently and have missed some threads. What I argued was that it would be easier to find the trace of a person's thoughts in a universe where he had a physically continuous record than where there were discontinuities (easier in the sense that a smaller program would suffice). In my framework, this means that the universe would contribute more measure to people who had continuous lives than people who teleported. Someone whose life ended at the moment of teleportation would have a higher measure than someone who survived the event. Therefore, I would view teleportation as reducing measure similarly to doing something that had a risk of dying. I would try to avoid it, unless there were compensating benefits (as indeed might be the case, just as people willingly accept the risk of dying by driving to work, because of the compensating benefits). You can say that "by definition" the person survives, but then, you can say anything by definition. I guess the question is, what is the reasoning behind the definition. As far as Lee's suggestion that people could be dying thousands of times a second, my framework does not allow for arbitrary statements like that. Given a physical circumstance, we can calculate what happens. It's not just arbitrary what we choose to say about life and death. We can calculate the measure of different subjective life experiences, based on the physical record. If we wanted to create a physical record where this framework would be compatible with saying that people die often, it would be necessary to physically teleport people thousands of times a second. Or perhaps the same thing could be done by freezing people for a substantial time, reviving them for a thousandth of a second, then re-freezing them again for a while, etc. If we consider the practical implications of such experiments I don't think it is so implausible to view them as being worse than living a single, connected, subjective life. It would be quite difficult to interact in a meaningful way with the world under such circumstances. However, if one were so unfortunate as to be put into such a situation, then it would no longer be particularly bad to teleport. You're being broken into pieces all the time anyway, so the event of teleportation would presumably not make things any worse. Particularly if you were somehow being teleported thousands of times a second, then adding a teleportation would basically be meaningless since you're teleporting anyway at every instant. So I don't agree with Lee's conclusion that in this situation people would still resist teleportation. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Fermi Paradox and measure
Ron Hale-Evans writes: > My favourite answer to the Fermi Paradox has been that the aliens are > using nearly-perfect compression or encryption for their radio signals > (if they're using radio), and that's why all we can detect is noise. > > However, tonight another "answer" occurred to me. What if we're living > in a finite simulation? I don't know that multiverse concepts explain the Fermi paradox, but they do cast it in a different light. As Bruno points out, our first-person experiences could be created by many different kinds of programs, corresponding to different "realities". It could be that everything is pretty much as it seems. Or perhaps we are living in a simulation controlled by aliens, or our descendants, or robots. Or it's even possible that everything is an illusion and we are in effect imagining it. All of these possibilities contribute to the measure of our experiences. So in some sense it must be simultaneously true that we are in a simulation, and that we are not in a simulation. Both situations exist in the multiverse and both contribute to the reality of our experiences. The hard part of the Fermi question still remains. It might be stated, why is the universe seemingly so large and so empty? In multiverse terms, why is the measure of observers who live in large, empty universes so large, compared to the measure of observers who live in universes teeming with life? For if the measure of the latter observers were much greater than the measure of the former, we would be highly unlikely to find ourselves one of that very small set of observers who see sparse universes. (Of course, I am skipping past the various conventional explanations that have been offered which allow for the universe to in fact be full of life but for it somehow not to be observable. Those have not been generally found to be convincing so we should focus on the hard part. Also, note that while I write "life" for short I really mean intelligent life.) A while back I speculated as follows. Presumably there are laws of physics which would lead to very densely populated universes. And we know that there are laws that lead to very sparse universes, like the ones we live in. All universes exist; all laws are instantiated. For various reasons many of us argue that universes with simpler laws are likely to be more common, to have larger measure. Now, we know that if the laws are too simple, life cannot exist. Trivial universes are not living ones. Presumably, as the laws get more complex, we pass a threshold where life can start to exist. But perhaps it is reasonable to assume that we will first find laws where life can barely exist, before we find laws where life is very common. If so, then there is a band of complexity where universes at the simple end of this band have very sparse intelligent life, and universes at the complex end have very dense intelligent life. Then, to be consistent with our observations, we have to conclude that this band is quite wide - that universes that are just barely complex enough for life have much simpler laws than universes that are teeming with life. That is how we would explain the fact that we find ourselves in one of the first kind. Their boost from having simpler laws must outweigh the increase in numbers of intelligent life forms in the more complex universes. I read that the universe is estimated to have about 10^23 stars. A universe with a high density of intelligent life might therefore be 10^23 times more densely populated than ours. This is about 2^75 times. Therefore we would predict that the physical laws necessary to create such a densely populated universe would be at least 75 bits longer than the simpler laws of our own universe. This is a prediction of multiverse theory as I interpret it. If it should turn out that there are very simple sets of laws that would create very numerous observers, then that would contradict the theory in this form. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Teleportation thought experiment and UD+ASSA
Bruno raises a lot of good points, but I will just focus on a couple of them. The first notion that I am using in this analysis is the assumption that a first-person stream of consciousness exists as a Platonic object. My aim is then to estimate the measure of such objects. I don't know whether people find this plausible or not, so I won't try to defend it yet. The second part, which I know is more controversial, is that it is possible to represent this object as a bit string, or as some similar, concrete representation. I think there are a couple of challenges here. The first is how to turn something as amorphous and intangible as consciousness into a concrete representation. But I assume that subsequent development of cognitive sciences will eventually give us a good handle on this problem and allow us to diagram, graph and represent streams of consciousness in a meaningful way. As one direction to pursue, we know that brain activity creates consciousness, hence a sufficiently compressed representation of brain activity should be a reasonable starting point as a representation of first-person experience. Another issue that many people have objected to is the role of time. Consciousness, it is said, is a process, not a static structure such as might be represented by a bit string. IMO this can be dealt with by interpreting the bit string as a multidimensional object, and treating one of the dimensions as time. See, for example, one of Wolfram's 1-D cellular automaton outputs: http://en.wikipedia.org/wiki/Image:CA_rule30s.png We see something that can alternatively be interpreted as a pure bit string; as a two-dimensional array of bits; or as a one-dimensional bit string evolving in time. In the same way we can capture temporal evolution of consciousness by interpreting the bit string as having a time dimension. An important point is that although there may be many alternative ways and notations to represent consciousness, they should all be isomorphic, and only a relatively short program should be necessary to map from one to another. Hence, the measure computed for all of these representations will be about the same, and therefore it is meaningful to speak of this as the measure of the experience as a platonic entity. Bruno also questioned my use of a physical universe in my analysis. I am not assuming that physical universes exist as the basis of reality. I only expressed the analysis in that form because we were given a particular situation to analyze, and that situation was expressed as events in a single universe. The Universal Dovetailer does not play a principle role in my analysis, because it does not play such a role in Kolmogorov complexity. At most, the Universal Dovetailer can be used as a heuristic device to explain what it might mean to "run all computatations" in order to explain K complexity. I think one difference between K complexity and Bruno's reasoning with the Universal Dovetailer is that the former focuses on sizes of programs while Bruno seems to work more in terms of run time. In the K complexity view, the measure of an information object is (roughly) 1/2^L, where L is the size of the shortest program which outputs that object. Equivalently, the measure of an information object is the fraction of all programs which output that object, where programs are sampled uniformly from all bit strings (or from whatever the input alphabet is for the UTM). This does not have anything to do with run time. Some bit patterns may have short programs that take a very long run time to output them. Such bit patterns are considered to have low complexity and high measure, despite the long run time needed. I think Bruno has sometimes said that the Universal Dovetailer makes some things have higher measure than others because they get more run time. I'm not sure how this would work, but it is a difference from the Kolmogorov complexity (aka Universal Distribution) view that I am using. Okay, those are some of the foundational questions and assumptions that I think are raised by Bruno's analysis. The rest of it goes through as I have described many times. Hal --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
RE: Re: Teleportation thought experiment and UD+ASSA
"Stathis Papaioannou" <[EMAIL PROTECTED]> writes: > OK, I think I'm clear on what you're saying now. But suppose I argue > that I will not survive the next hour, because the matter making up my > synapses will have turned over in this time. To an outside observer the > person taking my place would seem much the same, and if you ask him, he > will share my memories and he will believe he is me. However, he won't > be me, because I will by then be dead. Is this a valid analysis? My view > is that there is a sense in which it *is* valid, but that it doesn't > matter. What matters to me in survival is that there exist a person in > an hour from now who by the usual objective and subjective criteria we > use identifies as being me. The problem is that there seems to be no basis for judging the validity of this kind of analysis. Do we die every instant? Do we survive sleep but not being frozen? Do we live on in our copies? Does our identity extend to all conscious entities? There are so many questions like this, but they seem unanswerable. And behind all of them lurks our evolutionary conditioning forcing us to act as though we have certain beliefs, and tricking us into coming up with logical rationalizations for false but survival-promoting beliefs. I am attracted to the UD+ASSA framework in part because it provides answers to these questions, answers which are in principle approximately computable and quantitative. Of course, it has assumptions of its own. But modelling a subjective lifespan as a computation, and asking how much measure the universe adds to that computation, seems to me to be a reasonable way to approach the problem. > Even if it were possible to imagine another way of living my life which > did not entail dying every moment, for example if certain significant > components in my brain did not turn over, I would not expend any effort > to bring this state of affairs about, because if it made no subjective > or objective difference, what would be the point? Moreover, there would > be no reason for evolution to favour this kind of neurophysiology unless > it conferred some other advantage, such as greater metabolic efficiency. Right, so there are two questions here. One is whether there could be reasons to prefer a circumstance which seemingly makes no objective or subjective difference. I'll say more about this later, but for now I'll just note that it is often impossible to know whether some change would make a subjective difference. The other question is whether we could or should even try to overcome our evolutionary programming. If evolution doesn't care if we die once we have reproduced, should we? If evolution tells us to sacrifice ourselves to save two children, eight cousins, or 16 great-great uncles, should we? In the long run, we might be forced to obey the instincts built into us by genes. But it still is interesting to consider the deeper philosophical issues, and how we might hypothetically behave if we were free of evolutionary constraints. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
RE: Re: Only Existence is necessary?
"Stathis Papaioannou" <[EMAIL PROTECTED]> writes: > I am reminded of David Chalmer's paper recently mentioned by Hal Finney, > "Does a Rock Implement Every Finite State Automaton?", which looks at > the idea that any physical state such as the vibration of atoms in a > rock can be mapped onto any computation, if you look at it the right > way. Usually when this idea is brought up (Hilary Putnam, John Searle, > the aforementioned Chalmers paper) it is taken as self-evidently > wrong. However, I have not seen any argument to convince me that this > is so; it just seems people think it *ought* to be so, then look around > for a justification having already made up their minds. I tend to agree. People find the conclusion unpalatable and then they try to come up with some justification for why it is not true. As I mentioned, at least some people like, I think, Hans Moravec, accept the basic conclusion. > Now, if any > computation is implemented by any physical process, then if one physical > process exists, then all possible computations are implemented. I'll stop > at this point, although it is tempting to speculate that if all it takes > for every computation to be implemented is a single physical process - > a rock, a single subatomic particle, the idle passage of time in an > otherwise empty universe - perhaps this is not far from saying that the > physical process is superfluous, and all computations are implemented > by virtue of their existence as platonic objects. Yes, I think this is close to Moravec's view. He believes in the platonic existence of all conscious experiences, and sees the role of physical implementation as just to allow us to interact with those other entities who are instantiated in our universe. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Teleportation thought experiment and UD+ASSA
Russell Standish <[EMAIL PROTECTED]> writes: > If computationalism is true, then a person is instantiated by all > equivalent computations. If you change one instantiation to something > inequivalent, then that instantiation no longer "instantiates" the > person. The person continues to exist, as long as there remain valid > computations somewhere in the universe. And in almost any of the many > worlds variants we consider in this list, that will be true. That's true, but even with the MWI, making an instantiation cease to exist decreases the measure of that person. Around here we call that "murder". The moral question still exists. I don't see the MWI as rescuing functionalism and computationalism. What, after all, do these principles mean? They say that the implementation substrate doesn't matter. You can implement a person using neurons or tinkertoys, it's all the same. But if there is no way in principle to tell whether a system implements a person, then this philosophy is meaningless since its basic assumption has no meaning. The MWI doesn't change that. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
RE: Re: Teleportation thought experiment and UD+ASSA
"Stathis Papaioannou" <[EMAIL PROTECTED]> writes: > Hal Finney writes: > > I should first mention that I did not anticipate the conclusion that > > I reached when I did that analysis. I did not expect to conclude that > > teleportation like this would probably not work (speaking figurately). > > This was not the starting point of the analysis, but the conclusion. > > Yes, but every theoretical scientist hopes ultimately to be vindicated > by the experimentalists. I'm now not sure what you mean by the second > sentence in the above quote. What would you expect to find if (classical, > destructive) teleportation of a subject in Brussels to Moscow and/or > Washington were attempted? >From the third party perspective, I'd expect that we'd start with a person in Brussels, and end up with people in Moscow and Washington who each have the memories and personality of the person who is no longer in Brussels. The population of Earth would have increased by one. I imagine that this is unproblematic and is simply a restatement of the stipulated conditions of the experiment. The more interesting question to ask is whether I would submit to this, and if so, what would I expect? Note that this is not subject to experimental verification. When we have described the third party situation, we have already said everything that experimentalists could verify. When those two people wake up in Moscow and Washington there is no conceivable experiment by which we can judge whether the person in Brussels has in some sense survived, or perhaps has done even better than surviving. It's not even clear what these questions mean. It was my attempt to formalize these questions which led to my analysis. Perhaps it is best if I go back to the more formal statement of the results, and say that the contribution of this universe to the measure of a person who experiences surviving the teleportation and wakes up in W or M is much less than the contribution to the measure of a person who walks into the machine in Brussels and never experiences anything else. At a minimum, this would make me hesitant to use the machine. Now, other philosophical considerations might still convince me to use the machine; but it would be more like the two copies are my heirs, people who will live on after I am gone and help to put my plans into action. People sometimes sacrifice themselves for their children, and the argument would be even stronger here since these are far more similar to me than biological relations. So even if I don't personally expect to survive the transition I might still decide to use the machine. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Teleportation thought experiment and UD+ASSA
t, into whatever reprsentation we have chosen for the virtual world and qualia. Given that the universe created by the first part does evolve the brain states needed as input for the second part, the second part can be a relatively simple translation from physical to mental states. Therefore we can create a short program which outputs the virtual world and qualia in all its glory, and this short, two-part program will be the main contribution to the measure of that mental experience. Keep in mind that in this framework, we do not start with this two-part structure. The starting point is much simpler: all we want to know is, what is the Kolmogorov complexity of a mental experience? It is only once we begin analyzing the problem that we note as you did that building that mental experience as a universe of its own would require an enormously large program. And then we realize that we can make a much smaller program - with exactly the same output! - that has the two part structure I described here. We deduce that such a program is what is actually responsible for the measure of the experience. And from this we conclude that the contribution of a universe to the measure of a conscious experience is not the universe's measure itself, but that measure reduced by the measure of the program which outputs that conscious experience given the universe data as input. This then leads to the principle that a big brain in a small universe gets more of that universe's measure; that multiple instantiations of a consciousness within a universe mean more measure; and that fuzziness of the concept of an instantiation is no problem because it only affects the size of the numbers being multiplied together to get the measure contribution. As for the question above about the Universal Dovetailer universe, it is easily solved in this framework. The output of the UD is of essentially no help in producing the mental state in question, because the ouput is so enormous and we would have no idea where to look. Hence the UD does not make a dominant contribution to mental state measure and we avoid the paradox without any need for ad hoc rules. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Teleportation thought experiment and UD+ASSA
Russell Standish <[EMAIL PROTECTED]> writes: > On Tue, Jun 20, 2006 at 09:35:12AM -0700, "Hal Finney" wrote: > > I think that one of the fundamental principles of your COMP hypothesis > > is the functionalist notion, that it does not matter what kind of system > > instantiates a computation. However I think this founders on the familiar > > paradoxes over what counts as an instantiation. In principle we can > > come up with a continuous range of devices which span the alternatives > > from non-instantiation to full instantiation of a given computation. > > Without some way to distinguish these, there is no meaning to the question > > of when a computation is instantiated; hence functionalism fails. > > > > I don't follow your argument here, but it sounds interesting. Could you > expand on this more fully? My guess is that ultimately it will depend > on an assumption like the ASSA. I am mostly referring to the philosophical literature on the problems of what counts as an instantiation, as well as responses considered here and elsewhere. One online paper is Chalmers' "Does a Rock Implement Every Finite-State Automaton?", http://consc.net/papers/rock.html. Jacques Mallah (who seems to have disappeared from the net) discussed the issue on this list several years ago. Now, Chalmers (and Mallah) claimed to have a solution to decide when a physical system implements a calculation. But I don't think they work; at least, they admit gray areas. In fact, I think Mallah came up with the same basic idea I am advocating, that there is a degree of instantiation and it is based on the Kolmogorov complexity of a program that maps between physical states and corresponding computational states. For functionalism to work, though, it seems to me that you really need to be able to give a yes or no answer to whether something implements a given calculation. Fuzziness will not do, given that changing the system may kill a conscious being! It doesn't make sense to say that someone is "sort of" there, at least not in the conventional functionalist view. A fertile source of problems for functionalism involves the question of whether playbacks of passive recordings of brain states would be conscious. If not (as Chalmers and many others would say, since they lack the proper counterfactual behavior), this leads to a machine with a dial which controls the percentage of time its elements behave according to a passive playback versus behaving according to active computational rules. Now we can turn the knob and have the machine gradually move from unconsciousness to full consciousness, without changing its behavior in any way as we twiddle the knob. This invokes Chalmers' "fading qualia" paradox and is again fatal for functionalism. Maudlin's machines, which we have also mentioned on this list from time to time, further illustrate the problems in trying to draw a bright line between implementations and clever non-implementations of computations. In short I view functionalism as being fundamentally broken unless there is a much better solution to the implementation question than I am aware of. Therefore we cannot assume a priori that a brain implementation and a computational implementation of mental states will be inherently the same. And I have argued in fact that they could have different properties. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Teleportation thought experiment and UD+ASSA
Bruno writes: > Hal, > > It seems to me that you are introducing a notion of physical universe,=20 > and then use it to reintroduce a notion of first person death, so that=20 > you can bet you will be the one "annihilated" in Brussels. I should first mention that I did not anticipate the conclusion that I reached when I did that analysis. I did not expect to conclude that teleportation like this would probably not work (speaking figurately). This was not the starting point of the analysis, but the conclusion. The starting point was the framework I have described previously, which can be stated very simply as that the measure of an information pattern comes from the universal distribution of Kolmogorov. I then applied this analysis to specific information patterns which represent subjective, first person lifetime experiences. I concluded that the truncated version which ends when the teleportation occurs would probably have higher measure than the ones which proceed through and beyond the teleportation. Although I worked in terms of a specific physical universe, that is a short-cut for simplicity of exposition. The general case is to simply ask for the K measure of each possible first-person subjective life experience - what is the shortest program that produces each one. I assume that the shortest program will in fact have two parts, one which creates a universe and the second which takes that universe as input and produces the first-person experience record as output. This leads to a Schmidhuber-like ensemble where we would consider all possible universes and estimate the contribution of each one to the measure of a particular first-person experience. It is important though to keep in mind that in practice the only universe which adds non-negligible measure would be the one we are discussing. In other words, consider the first person experience of being born, living your life, travelling to Brussels and stepping into a teleportation machine. A random, chaotic universe would add negligibly to the measure of this first-person life experience. Likewise for a universe which only evolves six-legged aliens on some other planet. So in practice it makes sense to restrict our attention to the (approximately) one universe which has third-person objective events that do add significant measure to the instantiation of these abstract first-person experiences. > You agree that this is just equivalent of negating the comp hypothesis.=20 > You would not use (classical) teleportation, nor accept a digital=20 > artificial brain, all right? Do I miss something? It is perhaps best to say that I would not do these things *axiomatically*. Whether a particular teleportation technology would be acceptable would depend on considerations such as I described in my previous message. It's possible that the theoretical loss of measure for some teleportation technology would be small enough that I would do it. As far as using an artificial brain, again I would look to this kind of analysis. I have argued previously that a brain which is much smaller or faster than the biological one should have much smaller measure, so that would not be an appealing transformation. OTOH an artificial brain could be designed to have larger measure, such as by being physically larger or perhaps by having more accurate and complete memory storage. Then that would be appealing. I think that one of the fundamental principles of your COMP hypothesis is the functionalist notion, that it does not matter what kind of system instantiates a computation. However I think this founders on the familiar paradoxes over what counts as an instantiation. In principle we can come up with a continuous range of devices which span the alternatives from non-instantiation to full instantiation of a given computation. Without some way to distinguish these, there is no meaning to the question of when a computation is instantiated; hence functionalism fails. My approach (not original to me) is to recognize that there is a degree of instantiation, as I have described via the conditional Kolmogorov measure (i.e. given a physical system, how much does it help a minimal computation to produce the desired output). This then leads very naturally to the analysis I provided in my previous message, which attempted to estimate the conditional K measure for the hypothetical first-person computations that were being potentially instantiated by the given third-party physical situation. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Teleportation thought experiment and UD+ASSA
largest measure is contributed to first-person subjective records which span the whole range of lifetime from start to end. Arbitrary subsets of that subjective lifespan will have less measure than the whole thing. Now, back to B, W and M. As just discussed, the measure of B, which corresponds to a life which ends in Brussels, is likely to be relatively substantial. However this hypothetical teleporting or copying machine works, we stipulate that the guy who started in Brussels is not there a moment later. It's likely that a straightforward program which has been tracking neural events by virtue of their exceedingly slight impact on the Planck scale is going to be thrown off by this new process. Therefore a relatively simple program can output subjective record B. When we consider W and M (revivals in Washington and Moscow respectively) there is still probably a fairly small program that can produce those records. The main additional complication is that the program has to somehow be designed to be able to pick up the trail in the new city, to jump from recording neural events in Brussels to recording them in Washington or Moscow. This could be done in a couple of ways. The simplest would be to hard-code the location of the new version of the person, perhaps as a vector from the old one. But this could take quite a bit of information, as it might have to be accurate to the size of a synapse, a few nanometers. Probably a better way would be to track whatever physical event carries the causal signal from Brussels to the destination. Presumably something has to travel between the cities, carrying the information about the person, to allow him to be reconstructed at the destination(s). Whatever this effect or principle is, we could write a program which was able to follow this signal, as the neural activities in Belgium are being scanned or whatever. This would allow identifying the location of the new instance of the person, without having to hard-code the precise coordinates. The third-person universe data would tell us where to look. This would probably not be too complicated a program, but it is nevertheless going to be substantially larger than program B. B only had to track neural events. W and M have to be able to track both neural events and whatever physical principles are utilized by this copying and transmission process. W and M are therefore going to have to have two different analysis methods, compared to one for B. They should not have to be twice as big, since they don't have to actually track thought during the transmission (we assume that thought is suspended during that time), they just have to figure out where the new brain is being built. But chances are it is going to make W and M quite a bit larger than B. Compared to each other, W and M are probably almost identical. The only difference is that they make arbitrary different choices for which signal to follow in tracking the copying information, in order to find where the new instance is located. Maybe one has a 1 bit where the other has a 0. In all other respects the two programs are identical, and their measure should be the same. But, as noted above, B is substantially smaller, and as a result, B has a substantially larger measure. This means that the contribution of this third-person record of universe events to a subjective, first-person life experience that ends in Brussels is much larger than to an experience which continues in either Washington or Moscow. If we consider these as three hypothetical people, one who dies in Brussels, one who continues in Washington, and one who continues in Moscow, it is the first one who is instantiated to the substantially greatest degree by the operation of such a copying machine as we are considering. Informally, we could say that your most likely experience is that you will die in Brussels (bearing in mind the formal statement in the previous sentence). That is how I would analyze it based on computational principles. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Ascension (was Re: Smullyan Shmullyan, give me a real example)
Jesse Mazer writes: > The dovetailer is only supposed to generate all *computable* functions > though, correct? And the diagonalization of the (countable) set of all > computable functions would not itself be computable. The dovetailer I know does not seem relevant to this discussion about functions. It generates programs, not functions. For example, it generates all 1 bit programs and runs each for one cycle; then generates all 2 bit programs and runs each for 2 cycles; then generates all 3 bit programs and runs each for 3 cycles; and so on indefinitely. (This assumes that the 3 bit programs include all 2- and 1-bit programs, etc.) In this way all programs get run with an arbitrary number of cycles. These programs differ from functions in two ways. First, programs may never halt and hence may produce no fixed output, while functions must have a well defined result. And second, these programs take no inputs, while functions should have at least one input variable. What do you understand a dovetailer to be, in the context of computable functions? Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Reasons and Persons
Jesse Mazer writes: > I agree that Parfit's simple method would probably create a nonfunctional > state in between, or at least the intermediate phase would involve a sort of > split personality disorder with two entirely separate minds coexisting in > the same brain, without access to each other's thoughts and feelings. But > this is probably not a fatal flaw in whatever larger argument he was making, > because you could modify the thought experiment to say something like "let's > assume that in the phase space of all possibe arrangements of neurons and > synapses, there is some continuous path between my brain and Napoleon's > brain such that every intermediate state would have a single integrated > consciousness". There's no way of knowing whether such a path exists (and of > course I don't have a precise definition of 'single integrated > consciousness'), but it seems at least somewhat plausible. One way (perhaps the only way) I could see to do it would be for you to gradually acquire amnesia, then once you have forgotten your past, your personality could gradually change to match Napoleon's, then you could gradually recover memory of Napoleon's past. Whether such an extreme case would still support whatever conclusions Parfit seeks to draw, I don't know. You're never half-yourself and half-Napoleon. Rather, you sort of stop being anybody in the middle of the process. I don't think it makes any sense to suppose that you could be half-yourself and half-Napoleon. Certainly the physical process Russell quoted could never work, because there is no one-to-one correspondence between the neutrons in your brain and Napoleons. And each neutron has a distinctive shape. If you brought it over unchanged, it would intersect with and overlap other cells in the brain, and be non-functional. But if you change its shape, it won't be the same neuron in terms of its functional behavior. If you brought neurons over from Napoleon's brain but altered them in the process to match your own neurons physically and functionally, then you would never stop being yourself. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Smullyan Shmullyan, give me a real example
Bruno writes: > Meanwhile just a few questions to help me. They are hints for the=20 > problem too. Are you familiar with the following "recursive" program=20 > for computing the factorial function? > > fact(0) =3D 1 > fact (n) =3D n * fact(n - 1) > > Could you compute "fact 5", from that program? Could you find a similar=20 > recursive definition (program) for multiplication (assuming your=20 > machine already know how to add)? > Could you define exponentiation from multiplication in a similar way? =20 > Could you find a function which would grow more quickly than=20 > exponentiation and which would be defined from exponentiation like=20 > exponentiation is defined from multiplication? Could you generalize all=20 > this and define a sequence of more and more growing functions. Could=20 > you then diagonalise effectively (=3D writing a program who does the=20 > diagonalization) that sequence of growing functions so as to get a=20 > function which grows more quickly than any such one in the preceding=20 > sequence? Here's what I think you are getting at with the fairy problem. The point is not to write down the last natural number, because of course there is no such number. Rather, you want to write a program which represents (i.e. would compute) some specific large number, and you want to come up with the best program you can for this, i.e. the program that produces the largest number from among all the programs you can think of. If we start with factorial, we could define a function func0 as: func0(n) = fact(n) Now this gets big pretty fast. func0(100) is already enormous, it's like a 150 digit number. However we can "stack" this function by calling it on itself. func0(func0(100)) is beyond comprehension. And we can generalize, to call it on itself as many times as we want, like n times: func1(n) = func0(func0(func0( ... (n))) ... ))) where we have nested calls of func0 on itself n times. This really gets bigger fast, much faster than func0. Then we can nest func1: func2(n) = func1(func1(func1( ... (n))) ... ))) where again we have nested calls of func1 on itself n times. We know that func1(n) gets bigger so fast, func1(func1(n)) will get bigger amazingly faster, and of course with n of them it is that much faster yet. This clearly generalizes to func3, func4, Now we can step up a level and define hfunc1(n) = funcn(n), the nth function along the path from func1, func2, func3, Wow, imagine how fast that gets bigger. hfunc is for "hyperfunc". Then we can stack the hfuncs, and go to an ifunc, a jfunc, etc. Well, my terminology is getting in the way since I used letters instead of numbers here. But if I were more careful I think it would be possible to continue this process more or less indefinitely. You'd have program P1 which continues this process of stacking and generalizing, stacking and generalizing. Then you could define program P2 which runs P1 through n stack-and-generalize sequences. Then we stack-and-generalize P2, etc. It never ends. But it's not clear to me how to describe the process formally. So we have this ongoing process where we define a series of functions that get big faster and faster than the ones before. I'm not sure how we use it. Maybe at some point we just tell the fairy, okay, let me live P1000(1000) years. That's a number so big that from our perspective it seems like it's practically infinite. But of course from the infinite perspective it seems like it's practically zero. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: why can't we erase information?
A few years ago I posted a speculation about Harry Potter universes, from the Schmidhuber perspective. Schmidhuber argues that the reason we don't see such a universe is that its program would be more complex, hence its algorithmic-complexity measure would be less. Such a universe would basically have natural laws identical to what we see, but in addition it would have exceptions to the laws. You wave a wand and say "Lumino!" and light appears. (Here I am taking the Harry Potter name rather literally, but the same thing applies to the more general concept of universes with magical exceptions to the rules.) You could also argue, as Wei does, on anthropic grounds that in such a universe the ease of exploiting magic would reduce selection pressure towards intelligence. Indeed in the Harry Potter stories there are magical animals but it is never explained why their amazing powers did not allow them to dominate the world and kill off mundane creatures long before human civilization arose. I suggested that the Schmidhuber argument has a loophole. It's true that the measure of a simple universe is much greater than a universe with the same laws plus one or more exceptions. But if you consider the set of all universes built on those laws plus exceptions, considering all possible variants on exceptions, the collective measure of all these universes is roughly the same as the simple universe. So Schmidhuber gives us no good reason to reject the possibility that our universe may have exceptions to the natural laws. If we do live in an exceptional universe, we are more likely to live in one which is only "slightly" exceptional, i.e. one whose laws are among the simplest possible modifications from the base laws. Unfortunately, without a better picture of the true laws of physics and an understanding of the language that expresses them most simply, we can't say much about what form exceptions might take. We know that they would be likely to be simple, in the same language that makes our base laws simple, but since we don't know that language it is hard to draw conclusions. Here is where the anthropic argument advanced by Wei Dai sheds some light; one thing we could say is that these simple exceptions should not be exploitable by life and make things so easy as to remove selection pressure. So this would constrain the kinds of exceptions that could exist. Ironically, waving a wand and speaking in Latin would indeed be the kind of exception that would not likely be exploited by unintelligent life forms. So purely on anthropic principles we could not fully rule out Harry Potter magic. But the complexity of embedding Latin phrases in the natural laws would argue strongly against us living in such a universe. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re:why can't we erase information?
A few random thoughts: Not only can't you erase information, in the MWI I believe you can't create it either. The constancy of information is another way of expressing the QM principle of unitarity. I think it's also tied to time symmetry. Universes with time symmetry would be unable to create or destroy information. The MWI is time symmetric (that is, the Schrodinger equation is time symmetric). Wolfram investigated a variety of CA systems, some of which happened to be time symmetric. Generally I think those were more likely to create very regular patterns, while it was the time-asymmetric ones that were more likely to be chaotic and show interesting patterns. One advantage of being unable to destroy information is that it automatically makes learning and memory possible. These capabilities are probably necessary for the evolution of intelligence. It's not clear though that complete inability to destroy information is necessary for memory to work though. Perhaps if we favor simple universes, there is basically a choice between complete information preservation vs universes where it is not preserved well at all once you move above the Planck scale (e.g. information might be 0.999% preserved per Planck time step, which is not at all for our purposes). The idea of a universe where there are a few obscure loopholes that break the laws of physics is possible in this model, but somewhat unlikely. And there is no guarantee that the loopholes would be easy to find. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Indeterminism
Johnathan Corgan wrote: > Still, there is a certain appeal to shifting the question from "Why are > we conscious?" to "Consciousness doesn't exist, so why do we so firmly > believe that it does?" It is possible to imagine a machine that doubts (or perhaps I should say "doubts", i.e. we should not assume that it has doubts in the same way we do) whether it is conscious. Imagine a simple theorem-proving machine, one of Bruno's logic machines, complicated enough to have a representation of itself. We want to ask it if it is conscious. So we have to define consciousness in logical terms. That seems quite daunting. If we allow room for indeterminacy in our definitions, the machine might also have indeterminacy in its estimation of whether it is conscious. Or, imagine we meet aliens. How do we know if they are conscious? Or, turning it around, how would they know if they possess what humans call "consciousness"? How would we describe consciousness to them, who have very different brains and ways of information processing, such that they can know for sure whether they are conscious in the same way that humans are? The question of whether someone is conscious is far more problematic than is often supposed, given that we cannot even define consciousness! I tend to think that it is simply a convenient assumption, that everyone is conscious, to avoid facing up to the overwhelming difficulties that a true analysis of the question brings. The mere fact that we cannot define consciousness ought to be a pretty big red flag that we should not be making facile assumptions about who has it and who doesn't! (Or, if you say that we can in fact define consciousness, tell me how to know which AI programs have it, and which don't?) Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Solipsism (was: Numbers)
compute its measure and determine how big a contribution that part of the UD makes to our experiences. Likewise we could create a model of the solipsist universe, where only the person is real and all of his external experiences are provided by the program. It is very likely that it will turn out that the real-universe program will be much smaller than the solipsist one. The solipsist program has to have an enormous table to supply all of the sensory experiences a person will receive. It also needs to have some mechanism to compute his brain patterns, and probably the simplest will be to have an actual physical universe model. Building the brain patterns into an internal table is another way to do it but will probably be even larger. Any way you look at it, the solipsist program is going to be enormous. Reasoning in this way, we will not only be able to basically reject the solipsist hypothesis, we can actually do so in a quantitative way! We will be able to say, the fraction of your experiences due to the solipsist universe, or equivalently the probability that it is true, is this extremely tiny number. And it will very likely be an incredibly small number, 1/2^(10^20), perhaps. (I wrote a long posting last year which effectively estimated this number.) This, then, is an example of the power of the assumption about the platonic universe, that physical and mathematical reality are the same. It not only sheds light on ancient and seemingly insolvable conundrums such as solipsism, it should allow us to in principle produce quantitative estimates of the role of solipsist universes in the larger reality. If as I wrote yesterday we are able to eventually verify predictions of this model in terms of physical observations, we would have achieved a unification of physics and philosophy far deeper than has ever been accomplished before. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Re: Numbers
if they assume that our universe is just one of many; in some cases, one of an infinite number. If we end up accepting that an infinite number of universes "really" exist, having real physical reality, we are much closer to accepting that all informational objects exist. At least, it's much harder to argue that the notion that they are one and the same is absurd. Ideally, we could then start to make predictions based on this all-inclusive model which could be confirmed by experimental testing. Obviously we are a long way from being able to do that. I did make some predictions a few months ago when I was describing my own ideas along these lines, but they were pretty weak, and I had to make some strong assumptions, beyond just the basic multiverse model, to get them. Still, with further work I believe that it will be possible to come up with improved models and predictions that will allow various multiverse models to be tested. And it may yet turn out that the most inclusive multiverse, Tegmark's Level 4 where all mathematical objects exist and physical existence is just a subset of the mathematical, could be the model that provides the simplest explanation for our observations. Hal Finney --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~--~~~~--~~--~--~---
Multiverse concepts in string theory
n principle, a quantitative way of evaluating the measure of different universe models. Applying the anthropic principle we then derive the result that we should live in a universe which is about as simple as possible (i.e. has as high measure as possible) consistent with the evolution of life. One could then look at all of these string theory models, where no doubt some of them are very much simpler than others. The simpler ones would be the universes where we are most likely to live, if life is possible at all in them. Therefore the (near) infinity of possible models should not immediately be cause for dispair, but rather there is reason to hope that a model that defines the universe we actually live in may well be relatively simple, within the reach of a practical research program. Of course there are no guarantees of this. It could be that even though the complexity of our universe is small compared to infinity, it is still large compared to what human research could hope to achieve. We really don't have much basis to decide at this point, other than that the various attempts to explore relatively simple string theory models have all failed to describe a universe like ours. They do reveal universes with particles and force fields, but not ones that closely resemble our universe. And usually these hypothetical universes instantly explode or otherwise behave in a manner hostile to life. Of course, this level of analysis reminds us that there is no reason a priori that a variant of string theory has to be the correct model. As we know from Tegmark and Schmidhuber, among others, it is easy to generalize into a much wider set of possible universes. String theory has the nice feature that it creates a well-defined "particle zoo", i.e. a set of particles with particular masses, charges and other properties; and it is perhaps not so easy to pull that out of other models. But there are undoubedly at least some other ways to do it. And the truth is, we don't even know that the existence of particles as we observe them is truly as fundamental as string theory assumes. Particles could be an illusion, a manifestation of some deeper underlying phenomena. Unfortunately I think that in fairness we still have to classify most of these multiverse concepts as philosophy more than physics. Although we can come up with some in-principle predictions - such as that we will probably never discover a universe model that is much simpler than our own but which would evolve life - I don't know of any predictions that one could make based on anthropic reasoning that could be tested today. Physics is a science, and that means it needs to work with theories that can be tested and disproven. We are a long way from being able to come up with any experiment that a working physicist in his lab could run to see whether multiverse models are correct. (And no, quantum suicide doesn't count!) I also get the impression that Susskind's attempts to bring "disreputable" multiverse models into "holy" string theory is more likely to kill string theory than to rehabilitate multiverses. Perhaps I am getting a biased view by only reading this one blog, which opposes string theory, but it seems that more and more people are saying that the emperor has no clothes. If string theory needs a multiverse then it is even less likely to ever be able to make physical predictions, and its prospects are even worse than had been thought. A lot of people seem to be piling on and saying that it is time for physics to explore alternative ideas. The hostile NY Times book review is just one example. Hal Finney
Re: Paper+Exercises+Naming Issue
Here is a link to an article I wrote in 2001 explaining what the Universal Dovetailer is: http://www.mail-archive.com/everything-list@eskimo.com/msg01526.html Hal Finney
Re: Let There Be Something
Bruno writes: > OK. But the word "universe" can be misleading here. It is probably less > misleading to say that the Universal Dovetailer generates all > computations. By assuming comp, this generates also all the (first > person) observer-moments (states/worlds/...). > The physical reality will emerge from that, but there is no a priori > reason to believe the UD generates any particular physical reality, > although we have empirical reason that some quantum dovetailer will win > the "measure" battle. Isn't it hard, even assuming comp, to know whether a particular computation corresponds to a particular first-person observer-moment? Comp says that I am a computation, at some level of abstraction; but having faith in that principle will not tell me whether a given computation implements me. How can I bridge that gap? > If that means that my probable future, when I am in a comp state S, is > entirely determined by the collection of computations going through S, > with "intrinsical weight" determined by the UD (and thus by theoretical > computer science alone), then OK. Right, and the same question applies. To know if a given computation represents one of my first-person probable futures, I have to know quite a bit. I need to know how to go from a computation to a first-person experience; and I need to know details of my own first-person experiences so that I can judge whether a computation "matches" my experiences. That second part is obvious, I guess; I can be assumed to be aware of my own experiences. But the first part is what is hard, looking at a computation and deciding what kind of mind it creates. Do your theories offer insights into this hard part? Hal Finney
Re: Let There Be Something
Russell Standish writes: > It predicts that either a) there is no conscious life in a GoL > universe (thus contradicting computationalism) or b) the physics as > seen by conscious GoL observers will be quantum mechanical in nature. > > If one could establish that a given GoL structure is conscious, and > then if one could demonstrate that its world view is incompatible with > QM then we might have a contradiction.=20 > > Even then, there is still a loophole. I suspect that 3D environment > are far more likely to evolve the complex structures needed for > consciousness, so that conscious GoL observers are indeed a rare > thing. I don't know if this is the case or not, but if true it would > make a GoL example irrelevant. More interesting is to look at some 3D > CA rules that appear to support universal computation - Andy Wuensche > had a paper on this in last year's ALife in Boston. No arXiv ref I'm > afraid, but you could perhaps email him for an eprint... That's very interesting. Is it a matter of evolution, or mere existence? I can see that life would be hard to evolve naturally in Life - it's too chaotic. But it might well be possible for us to create a specially-designed Life "robot" which was able to move around and interact with a sufficiently well-defined and restrictive environment. How much constraint would your theories put on the capabilities of such a robot? Is it just that it could never be truly conscious? Or would your arguments limit its capabilities more strongly? Consciousness is hard to test for; would there be purely functional limitations that you could predict? Hal Finney
Re: Let There Be Something
Russell Standish writes: > Lack of convincing is perhaps due to lack of understanding. Even I do > not fully understand the true worth of my "derivation". It seems to me > that I show that any physical theory that takes into account > observation must have that Hilbert space structure, with that form of > the Born rule. Yet there may well be special conditions that nobody > has yet spotted that limit the claims. OTH, it cannot produce > something like the classic Schroedinger equation for the hydrogen > atom, which as we know must be strictly false as it ignores > relativistic effects. What about other universes, such as Conway's Life universe? It has nothing like QM. Does your argument predict that life is impossible in Life? We know that it is possible to create computers there - I think self-replicating machines as well. Can we really argue from such general premises that there is no way that living organisms could exist in that universe? I am skeptical that we can reach such strong and specific conclusions from such broad and general assumptions. Hal Finney
Re: Let There Be Something
Bruno Marchal writes: > And that illustrates the advantage of the comp theory, it gives by > construction the correct physics, without any need, for a comp > "believer" to verify it. Except, of course, that comp need to be > postulated and we must be open it is could be false. With comp, you > see, physics is approached in a radically different way. Different from > the 2300 years of Aristotelian Naturalism: comp makes us to go back to > Plato. Updtated by Godel's discoveries (and Church, Turing, etc.). Let me see if I understand how you construct the correct physics from comp. You start with the principle of the Universal Dovetailer, which creates all possible universes. You then examine those universes for subsystems which are consistent with your own first-person conscious experiences. You set up some kind of measure over this selected subset of universes. (The Universal Dovetailer perhaps implies the Universal Distribution.) And based on this measure you arrive at first-person indeterminacy about which laws of physics hold for you. Is that right, is that the mechanical procedure by which someone derives their laws of physics from comp? Hal Finney
Re: Let There Be Something
Stathis Papaioannou wrote: > We're very ambitious on this list, aiming for the One True Theory which will > explain the universe. It's fair enough to keep this in mind as the ultimate > goal, but you have to remember that every generation of scientists has > thought this goal was just in reach, no matter how simplistic and just plain > wrong their theories have turned out to be. It isn't just scientists who > have thought this way either; theologians and philosophers have also > regularly come up with Theories of Everything, or Everything Except a Few > Minor Details. Given this history, can we really be certain at the start of > the 21st century that our present knowledge and theories are somehow > fundamentally different to all that has come before? I don't think most of our versions of multiverse theories depend on the assumption that present-day physics is close to being right. It's true that we have some efforts such as those of Russell Standish to derive QM from a multiverse model, but (no offense to Russell) I don't think most of us have found those very convincing. If it should turn out that QM is not right, is only an approximation to a deeper theory, I don't think that would be seen as invalidating any of our models. In fact, I don't see present day physics as being very likely to be right, from the context of the multiverse theories I favor. I would expect our universe's physical laws to have a simple mathematical/computational formulation; in fact, they should be among the simplest such laws that could allow life and consciousness to evolve. Does string theory or LCG or other exotic variants of QM meet this criterion? It doesn't seem so, to me. In Wolfram's book A New Kind of Science he emphasizes the important role of simple computational systems (i.e. systems which can be simulated with short programs, which means that they would have a large measure in the Universal Distribution). Wolfram was trained as a physicist and he makes an effort to sketch a computationally oriented physical model that might be consistent with observation. IMO what he comes up with is highly complex and not particularly physical. In short, if there really exists a simple mathematical explanation of our universe, which IMO is a prediction of multiverse theories, I don't see our present physical models as being very close to that goal. That doesn't mean that multiverse theories are wrong, but it illustrates an inconsistency between multiverse models and the belief that we are "almost there" towards a ToE. Hal Finney
Re: Let There Be Something
n everything in biology (to our satisfaction). I don't see the relevance. Scientists of all stripes may find it useful to work at higher or lower levels of abstraction. That doesn't change the fact that it must all be grounded somewhere. > I should make another point, that it seems very likely that the worm > has no way of developing the in-apple technology to find out about > quantum mechanics or DNA. This emphasizes the fact that we, with our > quantum theories, M-theories, and loop gravity etc. could be just as > far away from explaining the universe as the worm is. It is true that we have created our physical theories based largely on experimentation with devices that could hardly be constructed by a worm in an apple. Yet I think most physicists would agree that there is no real alternative for describing even the ordinary, everyday universe based on simpler theories. As I described in the worm case, to really have a theory of biology we need cells; and to have a theory of cells we need atoms and molecules; and to have a theory of atoms and molecules we need subatomic particles; and we still need a theory of subatomic particles. Even though historically it did not work this way, in principle I believe that our common observations of the world are enough to deduce the laws of physics. At least, I am not aware of any alternative physics which would work and explain the commonplace world in great detail and precision, even if we leave out radioactivity and observations with microscope and telescope. So contrary to Quentin's point about Plato's allegory of the cave, I believe that even people in that situation, if they were intelligent enough, would be able to deduce the nature of the universe they were observing. Hal Finney
Re: Let There Be Something
Tom Caylor writes: > To look at this from a different perspective, suppose there was a worm that > lived in an apple, and the worm was super-intelligent to the point of being > able to grasp all of our mathematical concepts that Tegmark claims are > sufficient to describe all of reality. Then the worm asks, "Why is it that > I'm in > this apple?" Actually the apple is the whole of observed reality for the > worm, so it is equivalent to our observed universe. However the observABLE > universe for the worm is the same as our observable universe. Then the worm > comes > up with a multiverse theory along with a Wormopic Principle, saying that the > whole observable universe is just complex enough to sustain the inside of an > apple. Surely this must be true, since the worm can grasp all of > mathematics? The worm would come up with a multiverse theory that says that everything exists, including universes like ours with people, apple trees, apples and worms, and also including other universes which consist of just a single apple, possibly with a worm in it, and every other possibility besides. Among these possible universes there are a certain fraction which contain worms-in-apples consistent with the experiences, observations and memories that the worm has experienced in his own apple. He knows that he is one of those worms. He applies some kind of measure, such as the Universal Distribution, over all of these worms-in-apples and is able to come up with a probability distribution for which one he is. This results in first-person indeterminacy and uncertainty. It may well be that the simplest and most likely case is not a universe containing a single apple, but a universe like ours. The reason is that apples and worms are actually very complex objects at the cellular level, even more complex at the atomic level, and enormously complex at the sub-atomic Planck scale. The physics going on in the apple is every bit as complex as the physics of our own universe. Our universe has the advantage in that its initial condition was very simple - some say it was completely smooth and uniform in the initial instances of the Big Bang. Then we went along in a very natural and simple way and developed planets, where life evolved into apples and worms. The apple-only universe must create all this by fiat. It must be hard-wired into the initial conditions: everything about the apple, about the worm, and about the physics. It's very plausibly would take a more complex program to run a universe consisting of just an apple and a worm, than our whole universe where apples and worms evolve out of much simpler initial conditions. Hence the worm might well conclude that he is likely to be in a giant universe with billions of other apples and worms, as well as many other forms of life. Even though he has not yet observed any of these things, not yet having come to the surface of the apple, he can deduce it. But perhaps not. Suppose that this super-intelligent worm deduces that universes like ours are actually less likely than ones which are all apple. In that case, assuming that his reasoning is sound, then he is probably right. From the first-person perspective, when he chews up to the surface, he will probably find that he is indeed in an apple-only universe. The multiverse has many kinds of universes with worms in apples, and it may be that our own universe has only a small fraction of all the worms in apples, that most worms do in fact find themselves in other kinds of universes. That would be a possible conclusion of multiverse theory, and it might well be right. In short, there is no reason to expect a super-intelligent worm in an apple to come up with a different multiverse than the one we would, if we were also super-intelligent. We might be in different components of the multiverse than the typical worm, but that is not evidence against the theory or an example of a flaw in its explanatory power. Hal Finney
Re: Let There Be Something
Tom Caylor writes: > I believe that my statement before: > > >...simply bringing in the hypothetical set of all unobservable things > >doesn't explain rationally in any way (deeper than our direct > >experience) the existence of observable things. > > applies to the multiverse as well, since > the multiverse = observable things + unobservable things > and equivalently > the multiverse = this universe + unobservable things Are you saying that you don't agree that the anthropic principle applied to an ensemble of instances has greater explanatory power than when applied to a single instance? Hal Finney
Re: Let There Be Something
Tom Caylor writes: > I just don't get how it can be rationally justified that you can get > something out of nothing. To me, combining the multiverse with a > selection principle does not explain anything. I see no reason why it > is not mathematically equivalent to our universe appearing out of > nothing. I would suggest that the multiverse concept is better thought of in somewhat different terms. It's goal is not really to explain where the universe comes from. (In fact, that question does not even make sense to me.) Rather, what it explains better than many other theories is why the universe looks the way it does. Why is the universe like THIS rather than like THAT? Why are the physical constants what they are? Why are there three dimensions rather than two or four? These are hard questions for any physical theory. Multiverse theories generally sidestep these issues by proposing that all universes exist. Then they explain why we see what we do by invoking anthropic reasoning, that we would only see universes that are conducive to life. Does this really "not explain anything"? I would say that it explains that there are things that don't need to be explained. Or at least, they should be explained in very different terms. It is hard to say why the universe "must" be three dimensional. What is it about other dimensionalities that would make them impossible? That doesn't make sense. But Tegmark shows reasons why even if universes with other dimensionalities exist, they are unlikely to have life. The physics just isn't as conducive to living things as in our universe. That's a very different kind of argument than you get with a single universe model. Anthropic reasoning is only explanatory if you assume the actual existence of an ensemble of universes, as multiverse models do. The multiverse therefore elevates anthropic reasoning from something of a tautology, a form of circular reasoning, up to an actual explanatory principle that has real value in helping us understand why the world is as we see it. In time, I hope we will see complexity theory elevated in a similar way, as Russell Standish discusses in his Why Occam's Razor paper. Ideally we will be able to get evidence some day that the physical laws of our own universe are about as simple as you can have and still expect life to form and evolve. In conjunction with acceptance of generalized Occam's Razor, we will have a very good explanation of the universe we see. Hal Finney
RE: Quantum theory of measurement
Now that you are experts on this, try your hand on this FTL signalling device, <http://arxiv.org/abs/quant-ph?0204108>. The author, Daniel Badagnani, is apparently a genuine physicist, <http://cabtep5.cnea.gov.ar/particulas/daniel/pag-db.html>. Hal Finney
RE: Quantum theory of measurement
Ben Goertzel writes: > Hal, > > It won't make any difference, because the CC is not used in the way you > > imagine. It doesn't have to produce a record and it doesn't have to erase > > any records. > > OK, mea culpa, maybe I misunderstood the apparatus and it was not the CC > that records > things, but still the records > could be kept somewhere, and one can ask what would happen if the records > were > kept somewhere else (e.g. in a macroscopic medium). No? I don't think this makes sense, at least I can't understand it. > > The point is, there is no change to the s photon when we put the polarizer > > over by p. Its results do not visibly change from non-interference > > to interference, as the web page might imply. (If that did happen, > > we'd have the basis for a faster than light communicator.) No, all > > that is happening is that we are choosing to throw out half the data, > > and the half we keep does show interference. > > Yes but we are choosing which half to throw out in a very peculiar way -- > i.e. we are throwing it out by "un-happening" it after it happened, > by destroying some records that were only gathered after the events > recorded in the data already happened... You have to try to stop thinking of this in mystical terms. IMO people present a rather prosaic phenomenon in a misleading and confusing way, and this is giving you an incorrect idea. Nothing is un-happening. No records are destroyed after they were gathered. Forget that anybody told you this was a "quantum eraser" and think about what really happens. When all the polarizers are in place, half of the p photons get eaten and half get through. This gives us a way to split up the s measurements into two halves. It turns out that each half independently shows interference, but that the two interference patterns are the opposite of each other. When you combine the two halves back together, the peaks of one half fill in the valleys of the other, and the data set as a whole shows no interference. Look at it concretely as it might happen in the lab. We record a bunch of s measurements and also record whether we get a coincidence with a p photon getting through, in the CC. Maybe we write a little check mark next to the s measurements where there was a p photon coincidence. We go through afterwards to analyze the data. If we just plot all the s measurements we see a smooth curve, no interference. Now we go through and cross off the ones where there was no p coincidence. We cross off s measurement number 1, then numbers 3 and 4, then 5, 7, 10 through 12, and so on. When we plot the remaining measurements, now we see an interference pattern. In other words, the coincidence with the p photon identifies a subset of the s measurements which shows interference. The total collection of s measurements still shows no interference. There is no real "erasing" going on. Whoever coined the term "quantum eraser" was a master of public relations, but unfortunately he confused millions of lay people into getting the wrong idea about the physics. Hal Finney
Re: Quantum theory of measurement
Ben Goertzel writes about: > http://grad.physics.sunysb.edu/~amarch/ > > The questions I have regard the replacement of the Coincidence Counter (from > here on: CC) in the above experiment with a more complicated apparatus. > > What if we replace the CC with one of the following: > > 1) a carefully sealed, exquisitely well insulated box with a printer inside > it. The printer is hooked up so that it prints, on paper, an exact record > of everything that comes into the CC. Then, to "erase" the printed record, > the whole box is melted, or annihilated using nuclear explosives, or > whatever. The CC is not what is "erased". Rather, the so-called erasure happens to the photons while they are flying through the apparatus. Nothing in the experiment proposes erasing data in the CC. So I don't really see what you are getting at. > What will the outcome be in these experiments? It won't make any difference, because the CC is not used in the way you imagine. It doesn't have to produce a record and it doesn't have to erase any records. Let me tell you what really happens in the experiment above. It is actually not so mystical as people try to make it sound. We start off with the s photon going through a 2 slit experiment and getting interference. That is standard. Now we put two different polarization rotations in front of the two slits and interference goes away. The web page author professes amazement, but it is not really that surprising. After all, interference between two photons would typically be affected by messing with their polarizations. It is not all that surprising that putting polarizers into the paths could mess up the interference. But now comes the impressive part. He puts a polarizer in front of the other photon, the p photon, and suddenly the interference comes back! Surely something amazing and non-local has happened now, right? Not really. This new polarizer will eliminate some of the p photons. They won't get through. The result is that we will throw out some of the measurements of s photons, because if the p photon got eaten by its polarizer, the CC doesn't trigger as there is no coincidence. (This is the real reason for the CC in this experiment.) So now we are discarding some of the s photon measurements, and keeping some. It turns out that the ones we keep do show an interference pattern. If we had added back in the ones we discarded, it would blur out the interference fringes and there would be no pattern. The point is, there is no change to the s photon when we put the polarizer over by p. Its results do not visibly change from non-interference to interference, as the web page might imply. (If that did happen, we'd have the basis for a faster than light communicator.) No, all that is happening is that we are choosing to throw out half the data, and the half we keep does show interference. The only point of the CC, then, is to tell us which half of the data to throw out of the s photon measurements. Destroying the CC and all of the other crazy things you suggest have nothing to do with the experiment. The CC is not what is "erased" and it does not create a permanent record. It is only there to tell us whether a p photon got through its polarizer or not, so that we know whether to throw away the s photon measurement. Hal Finney
Re: What Computationalism is and what it is *not*
Bruno writes: > I will think about it, but I do think that CT and AR are just making > the YD more precise. Also everybody in cognitive science agree > explicitly or implicitly with both CT and AR, so to take them away > from YD could be more confusing. I think that is probably true about the Church Thesis, which I would paraphrase as saying that there are no physical processes more computationally powerful than a Turing machine, or in other words that the universe could in principle be simulated on a TM. I wouldn't be surprised if most people who believe that minds can be simulated on TMs also believe that everything can be simulated on a TM. (I don't see the two philosophical questions as absolutely linked, though. I could imagine someone who accepts that minds can be simulated on TMs, but who believes that naked singularities or some other exotic physical phenomenon might allow for super-Turing computation.) But isn't AR the notion that abstract mathematical and computational objects exist, to the extent that the mere potential existence of a computation means that we have to consider the possibility that we are presently experiencing and living within that computation? I don't think that is nearly as widely believed. That simple mathematical objects have a sort of existence is probably unobjectionable, but most people probably don't give it too much thought. For most, it's a question analogous to whether a falling tree makes a noise when there's no one there to hear it. Whether the number 3 existed before people thought about it is an abstract philosophical question without much importance or connection to reality, in most people's minds, including computationalists and AI researchers. To then elevate this question of arithmetical realism to the point where it has actual implications for our own perceptions and our models of reality would, I think, be a new idea for most computationalists. Right here on this list I believe we've had people who would accept the basic doctrines of computationalism, who would believe that it is possible for a human mind to be "uploaded" into a computer, but who would insist that the computer must be physical! A mere potential or abstractly existing computer would not be good enough. I suspect that such views would not be particularly rare among computationalists. Hal Finney
Re: What Computationalism is and what it is *not*
Bruno writes: > To sum up: comp is essentially YD, if only to provide a picture of > the first person comp indeterminacy. But CT is used to give a range > for that indeterminacy (the UD*, the trace of the UD). It is by CT > that the UD is really comp-universal, and it is a consequence of CT > that this forces it to dovetail, and to dovetail on an incredibly > redundant structures (providing non trivial relative measures). AR is > used to just accept the notion of UD* and other infinite mathematical > structures, and for justifying the use of the excluded middle principle. Okay, I was mostly trying to clarify the terminology. The problem is that sometimes you use "comp" as if it is the same as computationalism, and sometimes it seems to include these additional concepts of the Church Thesis and Arithmetical Realism. Maybe you should come up with a new word for the combination of comp (aka "Yes Doctor") + CT + AR. Then you could make it clear when you are just talking about computationalism, and when you are including the additional concepts. Hal Finney
Re: What Computationalism is and what it is *not*
Bruno wrote: > Of course the reversal result introduces ambiguity in expressions > like "mental activity". That is why I sum up "comp" by YD + CT + AR. > ("Yes doctor" + Church Thesis + Arithmetical realism). But if "comp" is computationalism, that is the doctrine that our mental processes can be modelled/reproduced by computational activity. This would seem to correspond to Bruno's "Yes Doctor". That is, you say "yes" to a doctor who wants to replace your mind with a computer, at least if it is done carefully and correctly. If you believe in computationalism, then you should believe that a computer could reproduce and substitute for the activity of your mind. (Some people have qualms about the details of the transfer process from the mind to the computer, but they are often satisfied if the change is done slowly, perhaps one neuron at a time.) Likewise if you would accept that your mind could be substituted by a computer, you are a computationalist. So where do the Church Thesis and Arithmetical realism come into play as part of the DEFINITION of "comp"? I don't understand this. Hal Finney
Re: subjective reality
I wade into this dispute with trepidation, because I think it is for the most part incomprehensible. But I believe I see one place where there was a miscommunication and I hope to clear it up. Godfrey Kurtz wrote, to Bruno Marchal: > You ARE doing something speculative whether you admit it or not! And I > don't really have to study your argument because > it is derived from premises that, you already admitted, are > incompatible with the conclusions you claim. What is this incompatibility? I believe he means it to be the following. Bruno had written: > This I knew. The collapse is hardly compatible with comp (and thus > YD). Even Bohm de Broglie theory, is incompatible with YD. And yet, Bruno claims that his methods will lead to a derivation of physics, which as far as we know includes QM. Godfrey sees the previous quote from Bruno as indicating that his "Yes Doctor" starting point is *incompatible* with QM. This is the contradiction that he sees. I'll stop here and invite Godfrey to comment on whether this is the admission of incompatibility between premises and conclusions that he was referring to above. Hal Finney
Re: Book preview: Theory of Nothing
I am a little confused about Russell's use of the term "self-aware". I have only had a chance to read a few pages of his book but I don't particularly see it defined in there. As Russell uses the term, is our normal, day to day state of consciousness "self-aware"? When I am reading, or watching TV, or eating, am I self-aware? I'm not sure how literally to interpret the phrase, whether seeing my foot makes me self-aware (since my foot is part of my self) but seeing my shoe does not? That's probably not right. It would be helpful to see how Russell distinguishes (or identifies) awareness, self-awareness, and consciousness for example. Hal Finney
Re: Maudlin's Machine and the UDist
to pin it down so that it depends on what happens merely on a particular world and its near neighbors, then that will not in general test the counterfactuals. If you expand it to include a wide range of possibilities, then there is too much going on, too many variations and bizarre outcomes, so that the criteria you are trying to use for consiciousness are met in some worlds and contradicted in others. All in all I don't think this approach will work as a general method for making consciousness supervene on physicality. Hal Finney
Re: Maudlin's Machine and the UDist
Russell Standish writes: > The take home message I get from Maudlin's experiment is that a > computationalist consciousness is supervenient on a physical process > _spread_ over the multiverse, ie the counterfactuals must really exist > as alternate branches of the Multiverse. So what does that tell you about Olympia? Is she conscious or not, by this criterion? I guess that you would say that if the unused counterfactual machinery would actually work if tested, then she is conscious; but if the counterfactual machines were broken or blocked such that they wouldn't work (even though they are not used) then she is unconscious. And perhaps you can say that the machines are in fact tested in other branches of the multiverse, so the criterion is more than merely a hypothetical difference between unused working machines and unused broken machines. I see some difficulties with this position but I better first hear whether this is what you have in mind before trying to extrapolate further. > A far as your UDist argument goes, the fact that a conscious HLUT, or > a conscious clock has very low measure simply means it is very > unlikely for us to be one of these things. They would still be > conscious. However accepting the Multiverse would eliminate these > objects from being conscious at all, because tof the lack of > counterfactuals. >From my perspective it doesn't make sense to ask whether a system is conscious, per se. Consciousness exists platonically in the multiverse. Any given consciousness exists, whether a particular system implements it or not. What we want to know is whether running a certain program or process will add to the measure of a given consciousness. Running a clock will not add any noticeable measure to any consciousness. Running a neural simulation or some AI program may well add significant measure. We can deduce these facts without considering counterfactuals. It is only necessary to see how short a program can compute a representation of the abstract conscious calculation by starting from the program or process that we initiate. My understanding is that the main argument for requiring counterfactuals in the definition of implementation is to escape the argument that a clock implements every finite state machine. I believe that other responses are better, such as the one by Jacques Mallah. Unfortunately Mallah's works seems to have largely disappeared from the web, as has Mallah himself, but I found an early copy of one of them on archive.org and have put it here, http://www.finney.org/~hal/mallah1.html. This version does not lay out the argument as clearly as the later ones, and merely hints at the role Kolmogorov complexity can play, but the basic ideas are present. Hal Finney
Maudlin's Machine and the UDist
, but still would contribute an appreciable measure. In any case, his machine certainly does not pose a challenge or paradox for the UDist framework, since UDist is merely a recipe for how to calculate a number, the measure of C. All kinds of bizarre machines might be imagined which would in some way relate to C, and still in principle we could estimate out how much measure they would each add to C. It seems that no paradox can arise from this type of analysis. Hal Finney
Re: OMs are events
Bruno writes: > Now an important fact is the following: computations themselves can be > seen as proofs. I have often seen this stated, but I'm not sure I have ever actually seen the construction. I could imagine turning a TM computation into a proof in the following way. There would be one axiom, which is the initial configuration of the TM: its initial tape, its head position, and its head state. Then the state transition table of the TM would correspond to rules of inference such that only one would apply at each state. Then starting with our one axiom, we go through successive lines of the proof, applying the single applicable rule of inference at each line, which exactly corresponds to what the TM would do at each state. > But with Church thesis, the notion of computation is > absolute: it does not depend on the formal system chosen (java = C = > turing = quantum computer = ...). So... a computation in one of these frameworks can be transformed into an equivalent computation in any other. > But provability is a relative notion > (like the notion of *total* (everywhere defined) computable functions. So in the case of the TM computation a theorem that is "provable" given the axioms and rules of inference would be a state that is "reachable" from the corresponding initial state and transition table. The question of whether a given theorem is "provable" is equivalent to asking whether a given computational state is ever reached. And of course that depends on precisely what computation is being done: on the specific program and data which are running. > To say "A is proved" has no meaning, you should always say: A is proved > in this or that theory (or by this or that machine). Right, if someone asked, does a program ever reach a state where x = 0? Then we must respond, which program? It is a meaningless question to ask unless we specify what program is running. That would be the corresponding statement, in computational terms. > Of course > provability can obey universal principles: for example the notion of > classical checkable proof in sufficiently rich system is completely > captured by the modal logics G and G*. Well, you lost me on that one! Hal Finney
Re: OMs are events
Brent Meeker wrote (he always forgets to forward to the list): > Hal Finney wrote: > > I'd be curious to know whether you think that Platonic existence could > > include a notion of time. > > I think timelessness is a defining characteristic of Platonic "existence". I > use scare quotes because I'm not sure what definition of "existence" would > justify ascribing existence of things like mathematical objects. Once we go > beyond our model of physical existence, we may have to invent various > categories > of "existence", e.g. "Dr. Watson exists in Sherlock Holmes stories". A Tegmark or Schmidhuber model in effect assumes that abstract, Platonic objects have enough existence for people to live in them. And in that case, there is no real difference between physical existence and Platonic existence. Physical existence would be a subset of Platonic. (Or as Bruno says, physical existence is a "modal" way of viewing Platonic existence, i.e. which objects are physically real would depend on the observer.) I know that not everyone here shares that view, however. If we consider the concept that "everything exists", the title of this list, then this does seem to lead us towards this merging of physical and mathematical/logical/Platonic existence. On the other hand, I would say that everything exists, but some things exist more than others. So I am drawing distinctions between degrees of existence (based on measure), and it may be that distinguishing physical from abstract existence is not such a dissimilar strategy. Hal Finney
Re: OMs are events
Brent Meeker writes: > I'm uncertain whether "instantiated by abstract mathematical patterns" means > that the patterns are being physically realized by a process in time (as in > the > sci-fi above) or by the physical existence of the patterns in some static > form > (e.g. written pieces of paper) or just by the Platonic "existence" of the > patterns within some mathematic/logic system. I'd be curious to know whether you think that Platonic existence could include a notion of time. Can you imagine a process, something that involves the flow of time, existing Platonically? Or would you restrict Platonic existence to things like integers and triangles, which seemingly don't involve anything like time? How about the case of mathematical proofs? Could an entire proof exist Platonically? A proof has a sort of time-like flow to it, causal dependency of later steps on earlier ones. It seems to be an interesting intermediate case. My tentative opinion is that it does make sense to ascribe Platonic existence to such things but I am interested to hear other people's thoughts. Hal Finney
Re: OMs are events
Quentin Anciaux writes: > Le Lundi 01 Août 2005 05:32, Hal Finney a écrit : > > I am generally of the school that considers that calculations can be > > treated as abstract or formal objects, that they can exist without a > > physical computer existing to run them. > > I completely agree with that... but I have problem with the word > "instantiating" in front of an abstract calculation, because if the > calculation is abtract that means the calculation just is, no need of > instantiation. I agree, and if I used that terminology then it was probably a mistake. Looking back at the message you replied to, I did not talk of instantiating an abstract calculation. I did mention the question of whether a given calculation instantiated a given OM. Maybe "instantiate" is not the right word there. I meant to consider the question of whether the first calculation added to the measure of the information structure corresponding to the OM. If you can find any other place where I used the word confusingly, let me know. > On the other hand I have still problem with abstract > calculation... take for example a mathematic demonstration written on a sheet > of paper, it doesn't mean anything if there is no observer to read it and > understand it (thereby "instantiating" the calculus in his own mind), what do > you think of that ? I can interpret your question in two ways. One is, does a mathematical proof written on paper has an intrinsic meaning, or is the meaning in the mind of the reader? And the other is, do mathematical proofs have abstract, logical/mathematical existence, in the same way that, say, numbers or geometric figures might be said to abstractly exist? As far as the first question, I would analyze it by asking whether someone who did not know the language it was written in, not even recognizing the symbols, would be able to deduce what the proof was. I believe the answer is yes, for reasonably long proofs. There would be no ambiguity. As a concrete way to understand this, suppose we want to ask the question, does this string of symbols represent proof X, where X is some valid mathematical proof. We could write a translation program which, given the symbols, would output proof X. If the string of symbols is reasonably long and actually does match proof X, the translation program will be short, much shorter than the proof itself. However if the string of symbols is not a proof of X, then the translation program will have to be long. By the same type of argument I have used repeatedly, this gives us a tool for evaluating whether a string has a given "meaning". If the translation program is short, then the meaning is in the string. If the translation program is long, then the meaning is in the translation. I believe that this shows that it is in fact reasonably to suppose that a complex proof written on paper does in fact have intrinsic meaning and it is not just a matter of how it is interpreted in the mind of the reader. In terms of the other question, whether proofs have abstract mathematical existence just as (we suppose) integers and triangles do, again I think that the answer is yes. Proofs are merely more complex. They have relationships amongs their parts. They depend on an axiom system. The implicit "causality" and "time ordering" among steps of the proof could be represented graphically, by colored arrows leading from one step to another. I could imagine a representation where valid proof steps would be as apparent and obvious as the question of whether a set of lines in a geometric figure all meet at a common point. In short, I do think that proofs, and for that matter computations, can be sensibly thought of as having abstract existence just like other complex mathematical objects. Some of the constructions of set theory are far more complex than any humanly understandable proof, yet it is reasonable to say that sets exist in the abstract. The fact that a proof has many parts and has complex relationships between the parts is no obstacle to its having abstract mathematical existence. Hal Finney
Re: OMs are events
Quentin Anciaux writes: > In all of these discussion, it is really this point that annoy me... What is > the calculation ? Is it a physical process ? Obviously a calculation need > time... what is the difference between an abstract calculation (ie: one which > is done on a sheet of paper or just in your head) with an "effective" > calculation ? What is the meaning of "instantiating" in a block universe > view ? I am generally of the school that considers that calculations can be treated as abstract or formal objects, that they can exist without a physical computer existing to run them. The goal is to model the universe (among other things) as such a calculation. If we demand that a calculation exists in a universe, and a universe is also a calculation, then we have an infinite regression. One might postulate a God who is infinite himself and is the endpoint of the regression, but absent such supernatural entities, the model otherwise doesn't work. Why model the universe as a calculation? Well, for one reason, because it seems to work. It appears that physical law is essentially mathematical, implying that it should be feasible in principle to construct a program which could simulate the entire universe to any degree of accuracy. It would seem odd, given that the universe can be a calculation, if it weren't a calculation. If it seems objectionable to have a calculation without a calculator, perhaps simpler examples can support the intuition. You can imagine a triangle without a triangulator. You can imagine a number without someone who counts. Perhaps you can even imagine a mathematical proof without a prover. Mathematical objects may have virtually unlimited complexity and internal structure, and can be said to exist independently of anyone who thinks about them or discovers them. Computations seem to fit very comfortably into this framework. If we allow ourselves to imagine calculations as having mathematical reality, and further to imagine that our universe is such a calculation, then we have unified mathematical and physical reality. There is no longer a difference. Things which are physically real are merely a subset of the things which are mathematically real. If we don't take this step, we have two kinds of reality, mathematical and physical, which makes for a more awkward (IMO) philosophical position. However I certainly understand that all these arguments are only persuasive and indicative and certainly do not amount to a proof. Nevertheless it is my hope that by pursuing these ideas we can construct testable propositions which, if verified, will add weight to the possibility that this is the nature of reality. Hal Finney
Re: OMs are events
o be embedded in a larger universe, and how that would affect the measure of the observer. That seems very much like your conception above, if I understood it correctly. > If I run a simulation of our solar system on a computer, then the > relevant events are e.g. that Jupiter is in such and such a position. This > is associated with the state of the transistors of the computer running the > program. But that same pattern could arise in a completely different > calculation. You would have to extract exactly what program is running on > the machine to be able to define OMs like that. To do that you need to feed > the program with different kinds of input and study the output, otherwise > you'll fall prey to the famous ''clock paradox'' (you can map the time > evolution of a clock to that of any object, including brains). I'm not sure I fully understand this, but I'll make two comments. First, a simulation of the solar system is vastly simpler than the calculation needed to create an observer. Intuitions based on the first case will fail when applied to the other. It may be plausible that two different calculations could create matching representations of Jupiter's orbit. But it's completely implausible that two calculations could accidentally both create the same sequence of observer moments. I estimated in the message above that the chance of that happening would be one in 2^(10^18). No human alive can even begin to grasp the impossibility of such an event. Think of the most absolutely, totally, completely impossible event you could ever imagine, and you won't be anywhere near as improbable as that. It is beyond human comprehension. Second, this clock paradox has been discussed before. Years ago Jacques Mallah on this list pointed out that algorithmic complexity disposes of it neatly. Sure, you can map any two calculations together, but if the map becomes bigger than the calculations, then all the correspondence is in the map and none in the calculations. In measure terms, it still comes down to how short a program you can write to produce the output that corresponds to an observer. Go ahead and write your clock or counter program, but its output does not match my canonical representation of an observer moment. The challenge is to write a translation program that turns the output of your clock into the OM's canonical representation (which is 10^18 bits in size!). Such a program is going to be as big as the OM data itself. The clock is of no help. On the other hand consider a program which (we would agree) really does output or create the observer-moment, but perhaps not in the nice canonical representation I might have defined. Then we can write a mapping program which will be relatively short, to turn one data representation into another. Even though we have 10^18 bits of data, the mapping program will still be much smaller than this, because its complexity does not depend on the size of the data to be translated. This shows that the program really did create the observer-moment, because there was little extra data in the map program. The correspondence was in the calculation, not in the map. With such large data sets as observer-moments, the point becomes very clear. There is effectively no ambiguity about whether a given calculation instantiates an OM or not. Clocks don't do it; neural network simulations can do it (with proper input); universe simulations can do it (using a subset of their output). Hal Finney
RE: What We Can Know About the World
ious by definition, there would still be virtually no "gray" there.) 5. To me, this points to the problem with panpsychism theories like this. On the one hand, everything is conscious (at least a little bit). This saves us from the Sorites paradox, that it's impossible to draw a line among shades of gray and try to separate white from black. But on the other hand, in practice only brains are noticeably conscious (and probably only big brains; the nematode with its 302 neurons can't have much consciousness). Even though our stomachs and earlobes are causal networks and have their little slivers of consciousness, only our brains manage to really count. It just seems strange that if consciousness is, in the metaphysical sense, so easy that it's omnipresent, then why do so few systems actually exhibit it? Hal Finney
UD, ASSA, QTI and DA
UD is the Universal Distribution, which assigns measure to information objects as the fraction of computer programs which output them on a given Universal Turing Machine. (I know I promised to use UDist for this acronym but I couldn't resist the title I chose.) ASSA is the Absolute Self Selection Assumption, which says that we should reason as though we are randomly selected observer moments (OMs). Combining the UD+ASSA means that the OMs should be selected according to the Universal Distribution. QTI is the Quantum Theory of Immortality, which says that in a many-worlds or multiverse model, each of us will experience immortality with certainty, because our deaths in some worlds will not affect the fact that we live on in others. The DA is the Doomsday Argument, which says (among other things) that the human race will not greatly increase in numbers beyond its present day size, because otherwise the chances that we would find ourselves so early in its history are insignificant. Here is an idea to tie these together. Some time back [1] I proposed that the measure of observer-moments would be amplified for those OMs which were remembered. Most OMs exist only transiently and are forgotten, but certain ones are special, make an impression, and are remembered for hours, days or even years. The measure of such OMs is arguably greater than the ones which are forgotten because of this effect. Let us assume that this is true and that in fact it can be a very strong effect, such that remembered OMs may acquire far more measure than forgotten ones. Then what does that suggest for the DA and QTI? One way to state the DA, using ASSA concepts, is to start with the supposition that the human race actually will vastly increase its numbers, perhaps spreading throughout the entire universe. Then we have to ask the question, how could it be that we are so early in its history? In measure terms, the total measure of late observer moments is vastly greater than the total measure of OMs as early as ours, so the odds are overwhelmingly against these OMs being experienced. Just as we accept the low measure of Flying Rabbit OMs as explaining the lawfulness of the universe, we should accept this way of expressing the DA as showing the contradiction in assuming that the human race will grow enormously. That is the conclusion of the DA, which some find paradoxical. The resolution could be to suppose that as the human race spreads, somehow it will retain a memory of its youth. The OMs that we are experiencing today will echo through time and gain measure in that way, via the remembering effect I discussed above. It could happen as literal memories, if we assume that somehow we will become personally immortal and create copies of ourselves who will spread throughout the universe and share in the vastening of the human race. Or perhaps a similar measure amplification effect could occur more indirectly; perhaps our mere influence on future events could leave sufficient traces down through time that present day OMs have much larger measure than future ones (on a per-OM basis). This would allow our present-day existence to be consistent with even a great vastening of humanity, resolving the DA. A similar argument might apply to the QTI. In ASSA terms, the conventional QTI does not work because the measure of extremely old versions of people is very small, so they would not be very prominent in the multiverse, any more than inhabitants of Flying Rabbit worlds. However, if the memory-amplification effect holds, then there could be a similar phenomenon to QTI. If we suppose that somehow certain people are destined for immortality, then the measure of even their young-age OMs would be greatly increased relative to their fellows by virtue of memory amplification. This would mean that those of us who are fortunate enough to have such destinies (which is not completely impossible today, given the progress of medical technology), would have very high-measure OMs. This implies that the experience of being a person is prima facae evidence that he may expect a much longer than usual life span, perhaps even an immortal existence. Such lucky individuals would have so much higher measure OMs even in their youth (due to memory amplification) that a randomly selected OM would very plausibly be that of such an individual. And the fact that we are young and not super-old is perhaps consistent as well, since younger OMs would have more memory amplification, both due to the fact that early experiences have more inherent distinctiveness and novelty because of youth, and due to the additional years they have to be remembered and for the echo effect to produce measure amplification. In short, finding onesself to be young is not necessarily an argument against this variant of the QTI, and may in fact be considered evidence in favor of a long or even immortal life span. Hal Finney [1] Near the end of http://www.escribe.com/sc
Reality in the multiverse
One problem with "reality" in the context of multiverse theories is that it may mean different things to different people. If we assume (for analytical purposes) that some form of multiverse exists, then ultimately the reality is the multiverse. But it seems that each person is constrained only to see one universe out of the multiverse. For him, that universe is all that is real, the rest of the multiverse is irrelevant. So already there is confusion over whether we should include the other worlds of the multiverse in "reality". I have been exploring the concept that the Universal Distribution exists and is "real". Reality in this model is every computer program execution, or equivalently (I would claim, but it is not too important here) every information pattern. This is a sort of "multiverse", in that it includes multiple "universes". Anything that can be created by a computer program exists, and arguably universes fall into this category. But it also includes other things. Chaotic information patterns that would not seem to possess most of the properties of a universe exist as well - without time, or causality, or dimensionality perhaps - just raw noise. And disembodied consciousnesses exist, too. We could each have our information patterns, the processes that make up our minds, be produced by programs which do not actually create the rest of the universe but simply contain hard-coded sense impressions which are delivered by clockwork. The UDist framework allows us to theoretically approximate the measure of these various information objects, so we can say that some are more "prominent" in the multiverse than others. But all exist, all are real, in this model. One of the points Bruno makes is that in these kinds of models, the reality for a given observer is pretty complicated. Much of the multiverse is irrelevant to him, but that doesn't mean he can focus on just one universe as "real". The observer spans multiple universes and multiple realities. In the UDist framework, I would say it in this way: Many programs create the information pattern corresponding to a given observer. Some of those programs create the observer as part of a relatively straightforward universe that corresponds fairly simply to his sense impressions. Some programs create the observer within a universe that has a far more subtle and complex relationship to what the observer senses. In some universes the observer is part of a simulation a la The Matrix, being run on artificial machines within that universe, so that what the observer sees has little relation to the "true reality" of that universe. And some programs create the information pattern as I described above, without a real universe at all, so that the observer in effect hallucinates the entire universe. The point is that all of these programs exist, hence all contribute measure to the observer. From the observer's perspective, all of these are in a sense "real" to him. However, he can in principle calculate (at least approximately) the numerical contribution made by each of these programs, and perhaps it turns out that the vast majority of the measure comes from just one of them. He might be justified in that case in largely ignoring the others and saying that only that one is "real" for him. But for full precision he must still take into consideration all of the programs that could create instances of his information pattern, and consider all of them to be "real" to some extent. And then, perhaps, he may choose to accept that the whole multiverse is real, even the parts which do not affect him. Otherwise he has to say that all programs exist which happen to include an information pattern corresponding to him, the observer who is making this claim. That's not a very compelling theoretical model. Hal Finney
Re: what relation do mathematical models have with reality?
Brent Meeker wrote: > [Hal Finney wrote:] > > When you observe evidence and construct your models, you need some > > basis for choosing one model over another. In general, you can create > > an infinite number of possible models to match any finite amount of > > evidence. It's even worse when you consider that the evidence is noisy > > and ambiguous. This choice requires prior assumptions, independent of the > > evidence, about which models are inherently more likely to be true or not. > In practice we use coherence with other theories to guide out choice. With > that kind of constraint we may have trouble finding even one candidate > theory. Well, in principle there still should be an infinite number of theories, starting with "the data is completely random and just happens to look lawful by sheer coincidence". I think the difficulty we have in finding new ones is that we are implicitly looking for small ones, which means that we implicitly believe in Occam's Razor, which means that we implicitly adopt something like the Universal Distribution, a priori. > We begin with an intuitive physics that is hardwired into us by > evolution. And that includes mathematics and logic. Ther's an excellent > little book on this, "The Evolution of Reason" by Cooper. No doubt this is true. But there are still two somewhat-related problems. One is, you can go back in time to the first replicator on earth, and think of its evolution over the ages as a learning process. During this time it learned this "intuitive physics", i.e. mathematics and logic. But how did it learn it? Was it a Bayesian-style process? And if so, what were the priors? Can a string of RNA have priors? And more abstractly, if you wanted to design a perfect learning machine, one that makes observations and optimally produces theories based on them, do you have to give it prior beliefs and expectations, including math and logic? Or could you somehow expect it to learn those? But to learn them, what would be the minimum you would have to give it? I'm trying to ask the same question in both of these formulations. On the one hand, we know that life did it, it created a very good (if perhaps not optimal) learning machine. On the other hand, it seems like it ought to be impossible to do that, because there is no foundation. > > Mathematics and logic are more than models of reality. They are > > pre-existent and guide us in evaluating the many possible models of > > reality which exist. > I'd say they are *less* than models of reality. They are just consistency > conditions on our models of reality. They are attempts to avoid talking > nonsense. But note that not too long ago all the weirdness of quantum > mechanics and relativity would have been regarded as contrary to logic. I guess we could agree that they are "other" than models of reality? It still strikes me as paradoxical: ultimately we have learned our intuitions about mathematics and logic from reality, via the mechanisms of evolution and also our own individual learning experiences. And yet it seems that at some level a degree of logic, and certain mathematical assumptions, are necessary to get learning off the ground in the first place, and that they should not depend on reality. I'm pretty confused about this right now. Hal Finney
Re: what relation do mathematical models have with reality?
Stephen Paul King wrote: > BTW, Scott Aaronson has a nice paper on the P=NP problem that is found here: > http://www.scottaaronson.com/papers/npcomplete.pdf That describes different proposals for physical mechanisms for efficiently solving NP-complete problems: things like quantum computing variants, relativity, analog computing, and so on. He actually looked at a claim that soap bubble films effectively solve NP complete problems and tested it himself, to find that they don't work. He also discusses time travel and even what we call quantum suicide, where you kill yourself if the machine doesn't guess right. I am skeptical though about something he says in conclusion: "Even many computer scientists do not seem to appreciate how different the world would be if we could solve NP-complete problems efficiently If such a procedure existed, then we could quickly find the smallest Boolean circuits that output (say) a table of historical stock market data, or the human genome, or the complete works of Shakespeare. It seems entirely conceivable that, by analyzing these circuits, we could make an easy fortune on Wall Street, or retrace evolution, or even generate Shakespeare's 38th play. For broadly speaking, that which we can compress we can understand, and that which we can understand we can predict if we could solve the general case - if knowing something was tantamount to knowing the shortest efficient description of it - then we would be almost like gods." This doesn't seem right to me, the notion that an NP solving oracle would be able to find the shortest efficient description of any data. That would require a more complex oracle, one that would be able to solve the halting problem. I think Aaronson is blurring the lines between finding the smallest Boolean circuit and finding the smallest efficient description. Maybe finding the smallest Boolean circuit is in NP; it's not obvious to me but it's been a while since I've studied this stuff. But even if we could find such a circuit I'm doubtful that all the rest of Aaronson's scenario follows. Hal Finney
Re: what relation do mathematical models have with reality?
Forwarded on behalf of Brent Meeker: > On 24-Jul-05, you wrote: > > > Brent Meeker writes: > >> Here's my $0.02. We can only base our knowledge on our experience > >> and we don't experience *reality*, we just have certain > >> experiences and we create a model that describes them and > >> predicts them. Using this model to predict or describe usually > >> involves some calculations and interpretation of the calculation > >> in terms of the model. The relation of the model to reality, if > >> it's a good one, is it gives us the right answer, i.e. it > >> predicts accurately. Their are other criteria for a good model > >> too, such as fitting in with other models we have; but prediction > >> is the main standard. > > > > This makes sense but you need another element as well. This shows up > > most explicitly in Bayesian reasoning models, but it is implicit in > > others as well. That is the assumption of priors. > > > > When you observe evidence and construct your models, you need some > > basis for choosing one model over another. In general, you can create > > an infinite number of possible models to match any finite amount of > > evidence. It's even worse when you consider that the evidence is noisy > > and ambiguous. This choice requires prior assumptions, independent of the > > evidence, about which models are inherently more likely to be true or not. > > In practice we use coherence with other theories to guide out choice. With > that kind of constraint we may have trouble finding even one candidate > theory. We begin with an intuitive physics that is hardwired into us by > evolution. And that includes mathematics and logic. Ther's an excellent > little book on this, "The Evolution of Reason" by Cooper. > > > > > > This implies that at some level, mathematics and logic has to come before > > reality. That is the only way we can have prior beliefs about the models. > > Whether it is the specific Universal Priori (1/2^n) that I have been > > describing or some other one, you can't get away without having one. > > > >> So in my view, mathematics and theorems > >> about computer science are just models too, albeit more abstract > >> ones. Persis Diaconsis says, "Statistics is just the physics of > >> numbers." I have a similar view of all mathematics, e.g. > >> arithmetic is just the physics of counting. > > > > I don't think this works, for the reasons I have just explained. > > Mathematics and logic are more than models of reality. They are > > pre-existent and guide us in evaluating the many possible models of > > reality which exist. > > I'd say they are *less* than models of reality. They are just consistency > conditions on our models of reality. They are attempts to avoid talking > nonsense. But note that not too long ago all the weirdness of quantum > mechanics and relativity would have been regarded as contrary to logic. > > > Brent Meeker
Re: what relation do mathematical models have with reality?
Brent Meeker writes: > Here's my $0.02. We can only base our knowledge on our experience > and we don't experience *reality*, we just have certain > experiences and we create a model that describes them and > predicts them. Using this model to predict or describe usually > involves some calculations and interpretation of the calculation > in terms of the model. The relation of the model to reality, if > it's a good one, is it gives us the right answer, i.e. it > predicts accurately. Their are other criteria for a good model > too, such as fitting in with other models we have; but prediction > is the main standard. This makes sense but you need another element as well. This shows up most explicitly in Bayesian reasoning models, but it is implicit in others as well. That is the assumption of priors. When you observe evidence and construct your models, you need some basis for choosing one model over another. In general, you can create an infinite number of possible models to match any finite amount of evidence. It's even worse when you consider that the evidence is noisy and ambiguous. This choice requires prior assumptions, independent of the evidence, about which models are inherently more likely to be true or not. This implies that at some level, mathematics and logic has to come before reality. That is the only way we can have prior beliefs about the models. Whether it is the specific Universal Priori (1/2^n) that I have been describing or some other one, you can't get away without having one. > So in my view, mathematics and theorems > about computer science are just models too, albeit more abstract > ones. Persis Diaconsis says, "Statistics is just the physics of > numbers." I have a similar view of all mathematics, e.g. > arithmetic is just the physics of counting. I don't think this works, for the reasons I have just explained. Mathematics and logic are more than models of reality. They are pre-existent and guide us in evaluating the many possible models of reality which exist. Hal Finney
Re: what relation do mathematical models have with reality?
Colin Hales writes: > The idea brings with it one unique aspect: none of the calculii we > hold so dear, that are so wonderful to play with, so poweful in their > predictive nature in certain contexts, are ever reified. None of them > actually truly capture reality in any way. They only appear to in > certain contexts. The only actual mathematics that captures the true > nature of the universe is the universe itself as a calculus. It doesn't > invalidate the maths we love. It just makes it merely a depiction in a > certain context. Very useful but thats all. You might like this quote from John Wheeler, in his textbook Gravitation written with Charles Misner and Kip Thorne, which perhaps expresses a similar idea: : Paper in white the floor of the room, and rule it off in one-foot : squares. Down on one's hands and knees, write in the first square : a set of equations conceived as able to govern the physics of the : universe. Think more overnight. Next day put a better set of equations : into square two. Invite one's most respected colleagues to contribute : to other squares. At the end of these labors, one has worked oneself : out into the door way. Stand up, look back on all those equations, : some perhaps more hopeful than others, raise one's finger commandingly, : and give the order `Fly!' Not one of those equations will put on wings, : take off, or fly. Yet the universe 'flies'. My current view is a little different, which is that all of the equations "fly". Each one does come to life but each is in its own universe, so we can't see the result. But they are all just as real as our own. In fact one of the equations might even be our own universe but we can't easily tell just by looking at it. Hal Finney
UDist and measure of observers
icrosecond and a nanometer for producing a description of a brain. The actual analysis software should be straightforward. We need to locate all the neurons, record their interconnection patterns, and then their firing rates and activity levels. All of these have relatively simple physical correlates given that you can analyze matter at an arbitrarily fine scale. Locating the neurons can be done by tracing their outer membranes. The interconnection patterns should be determined by the amount of area they have in common, the number and distribution of vessicles and receptors in the area, and basic chemistry as to whether the connection is inhibitory or excitatory. This is a matter of simple geometry and counting. Likewise, the activity level is a function of the concentration of various chemicals inside vs outside the neural membrane and can be calculated very simply. This level of software is adequate to create the data structure defined above for completely specifying the neural activity which corresponds to a given set of observer moments. It amounts to simple counting, area calculation, and averaging. My guess again is that 10^4 to 10^5 bits is fully adequate to perform these tasks. Adding the < 10^3 bits needed to localize the observer still keeps it within this range. Combining the software to create the universe, perhaps 10^4 bits, and the software to output the observer description, about 10^4 to 10^5 bits, we get the size proposed above, 10^4 to 10^5 bits for a self-contained program which will output the observer description in question. On this basis we can use a number like 1/2^(10^4) as an estimate for the measure of such a set of observer moments. Hopefully this explanation will clarify how we can apply the UDist model to calculate measure of observer moments as well as other information structures. It also illustrates how far we are from the scientific knowledge necessary to come up with more precise estimates for the information content of conscious entities. Nevertheless, even with the crude level of knowledge available today, we can make many powerful predictions from this kind of model. One case described above is the paradox of whether conscious entities exist all around us due to vibrations in air molecules, which this analysis lets us reject in a quantitative sense. Hans Moravec in particular has argued that such entities have a reality equal to our own, which is clearly wrong. A similar analysis disposes of the long standing philosophical debate over whether a clock implements every finite state machine (and hence every conscious entity). Other puzzles, such as the impact on measure of replays and duplicates can also be addressed and solved in this framework. I have described other predictions and solutions in my earlier messages on this topic. Again, I hope that by laying out my calculations in this much detail it will help people to see somewhat concretely how the Universal Distribution works and how you can analyze measure using actual software engineering concepts. It makes the UDist much more real as a useful tool for understanding measure and making predictions. Hal Finney
Re: is induction unformalizable?
Wei Dai writes: > 1. P=?NP is a purely mathematical problem, whereas the existence of an HPO > box is an emperical matter. If we had access to a purported HPO box while > P=?NP is still unsolved, we can use the box to exhaustively search for > proofs of either P=NP or P 2. I think it's very unlikely that P=NP, but in case it is, we can still > test an HPO box by generating random instances of hard problems with known > solutions. (That is, you generate a random solution first, then generate a > random problem with that solution in mind.) For example here's a page about > generating random instances of the Traveling Salesman Problem with known > optimal solutions. > > http://www.ing.unlp.edu.ar/cetad/mos/FRACTAL_TSP_home.html That's a good idea, but is it known that this subset of problems is still NP-hard? I would worry that problems like these, where a fractal or space-filling curve type of path is the right solution, might turn out to be easier to solve than the general case. Hal Finney
Re: The Time Deniers and the idea of time as a "dimension"
George Levy writes: > Hal Finney wrote: > >http://space.mit.edu/home/tegmark/dimensions.html , specifically > >http://space.mit.edu/home/tegmark/dimensions.pdf . > > Wouldn't it be true that in the manyworld, every quantum branchings that > is decoupled from other quantum branchings would in effect define its > own time dimension? The number of decoupled branchings contained by the > observable universe is very large. Linear time is only an illusion due > to our limited perspective of the branching/merging network that our > consciousness traverses. While our consciousness may spread over > (experience) several OMs or nodes in that network, it can only perceive > a single path through the network. Tegmark's idea of multiple time dimensions was more general than this. As with multiple space dimensions, you could travel about in the time dimensions. In relativity theory, there is a "light cone" that restricts which direction is "forward" in time. You can change your direction but are constrained to always be going forward relative to your light cone. This keeps you from turning around and going backwards in time, because you can't exceed the speed of light. However with 2 dimensional time the geometry is different and you actually go backwards in time. Your own personal clock goes forward but you can end up back before you started. I'll give you a mental visualization you might find useful and interesting. There is a conventional way to think of a light cone which is what gives it its name. Imagine a 2+1 dimensional universe, 2 spatial dimensions and 1 of time. To think of it, start with an x-y plane with the x and y axes. We'll call the y axis time, positive being upward. This is a 1+1 dimensional universe. Now imagine the lines x=y and x=-y, in other words the two lines running at 45 degrees and crossing at the origin. These can be thought of as the paths of light rays emitted by or received at the origin. Now imagine spinning the whole thing around the y axis, where the new z axis will be another spatial dimension. The crossed lines become a pair of cones that represent possible light beams being emitted from or received at the origin. These are called light cones. At each point in space we could imagine a pair of such cones existing, future and past. Objects are constrained in their movements to only be going upward, they have to stay within their light cones. Now for the variant, with a 1+2 dimensional universe: 1 spatial dimension and 2 time dimensions. Again we will start with the x-y plane, y is time, and we draw the crossed 45 degree lines. This time we spin around the x axis, to again produce two cones, but they are pointed right and left rather than up and down. In this model z is a time dimension like y, so we have 2 time dimensions. Now, objects again are constrained in their movements not to cross the cones, but the cones are pointed to the side rather than upward. This means that objects are not stuck inside the cones but are in effect outside of them and are able to move much more freely. You can see perhaps how an object could start at the origin, move in a loop in the y-z plane and return to the origin, all without ever passing through the cones. This is the nature of the 2-dimensional time explored by Tegmark. It is pretty different from the MWI. I would not say that the MWI has multidimensional time any more than it has >3 dimensional space. Technically the MWI all happens in one spacetime area, it is all superimposed and squashed together. There is merely a mathematical separation which occurs when states become decoherent, such that their future histories are causally independent. But technically they are still using the same space and time, they are just invisible to each other. Hal Finney
RE: The Time Deniers and the idea of time as a "dimension"
Physicist Max Tegmark has an interesting discussion on the physics of a universe with more than one time dimension at http://space.mit.edu/home/tegmark/dimensions.html , specifically http://space.mit.edu/home/tegmark/dimensions.pdf . In the excerpts below, n is the number of space dimensions and m the number of time dimensions, so when he writes m > 1 he means more than one time dimension. Quoting Tegmark: : What would reality appear like to an observer in a manifold with more : than one time-like dimension? Even when m > 1, there is no obvious : reason why an observer could not, none the less, perceive time as being : one-dimensional, thereby maintaining the pattern of having "thoughts" : in a one-dimensional succession that characterizes our own reality : perception. If the observer is a localized object, it will travel along : an essentially one-dimensional (time-like) world line through the (n + : m)-dimensional spacetime manifold. The standard general relativity notion : of its proper time is perfectly well defined, and we would expect this : to be the time that it would measure if it had a clock and that it would : subjectively experience. : : Needless to say, many aspects of the world would none the less appear : quite different. For instance, a re-derivation of relativistic mechanics : for this more general case shows that energy now becomes an m-dimensional : vector rather than a constant, whose direction determines in which : of the many time directions the world line will continue, and in the : non-relativistic limit, this direction is a constant of motion. In : other words, if two non-relativistic observers that are moving in : different time directions happen to meet at a point in spacetime, they : will inevitably drift apart in separate time directions again, unable : to stay together. : : Another interesting difference, which can be shown by an elegant : geometrical argument [10], is that particles become less stable when m : > 1 : : In addition to these two differences, one can concoct seemingly strange : occurrences involving "backward causation" when m > 1. None the less, : although such unfamiliar behaviour may appear disturbing, it would seem : unwarranted to assume that it would prevent any form of observer from : existing. After all, we must avoid the fallacy of assuming that the : design of our human bodies is the only one that allows self-awareness : : There is, however, an additional problem for observers when m > 1, : which has not been previously emphasized even though the mathematical : results on which it is based are well known. If an observer is to be : able to make any use of its self-awareness and information-processing : abilities, the laws of physics must be such that it can make at least : some predictions. Specifically, within the framework of a field theory, : it should, by measuring various nearby field values, be able to compute : field values at some more distant spacetime points (ones lying along its : future world line being particularly useful) with non-infinite error : bars. If this type of well-posed causality were absent, then not only : would there be no reason for observers to be self-aware, but it would : appear highly unlikely that information processing systems (such as : computers and brains) could exist at all. Tegmark then goes into quite a technical discussion about solving the equations of physics given various ways of specifying initial values, the upshot of which is that if m > 1 (i.e. more than one time dimension) observers would not be able to predict the state in the rest of the universe from their observations, which would seem to preclude the existence of observers. I'm not sure I fully understood this argument. However the earlier part is quite instructive in giving us a picture of how a universe could look that had multiple time dimensions. Any one entity would still have a single time line, but different ones might disagree about which direction the future was, and time loops would be possible. Personally I think this is a more serious problem than Tegmark's idea about prediction difficulties, although he seems to gloss over it as mere unfamiliar behavior. Nevertheless I think it is instructive to realize that multiple time dimension universes are a conceptual possibility even if they are unlikely to contain observers like us. Tegmark is implicitly writing within the block universe perspective which is generally adopted by physicists. Translating this into a "flow of time" view seems quite challenging and suggests that that viewpoint may not be as flexible in terms of deep understanding of the notion of time. Hal Finney
Problems with the Universal Distribution
bserver within an MWI universe is exponentially greater than in a simple universe, and that implies that the size of the locating program described above changes from small to enormous. The consequence is that the contribution of an MWI that contains an observer to that observer's measure appears to be essentially zero. The observer is just too small a fraction of the MWI, or in other words, the MWI is so profligate in its creation of universes that each individual branch has essentially zero measure. (This objection was also pointed out originally by Wei Dai.) Well, there are several possible solutions to this, none of them terribly attractive. One is the possibility that our measures within the MWI are much higher than they seem, because somehow our existence is much more inevitable than we would suppose. Rather than all the quantum branches producing totally different worlds, somehow most of them produce worlds with us in them, the specific people on this list, Bruno and Russell and all the others. It may seem absurd or bizarre, but I suppose it's not impossible. In that case we occupy many of the quantum branches rather than an infinitesimal fraction of them, and our measures in the MWI are high. A more attractive solution is that the MWI is false, or more precisely, that most of our measure comes from universes with true state reduction, with essentially none coming from universes that don't reduce states, where the MWI would be true. The biggest problem with this one for me is that I don't know of any QM interpretations other than the MWI that are truly coherent. Certainly Copenhagen isn't; it doesn't define precisely when state reduction occurs. Maybe some of the other ones, Cramer's or Bohm's, can be made to work. In this case, ironically, a multiverse model could be taken to disprove the MWI. The really weird part of this solution is that for it to work, for the universe program to be small, quantum randomness can't be truly random. Otherwise the program for the universe would have to be loaded up with random bits, one for each quantum state reduction, and it would be enormous. No, the only way this can work is for quantum randomness to be generated by a numeric pseudo random number generator (PRNG). We all live in von Neumann's "state of sin". I guess this is the AUH version of original sin. Plus it means that we are pretty special after all. Each different seed for the PRNG, each variant on a PRNG, would generate a different version of this universe, each with its own set of observers. Probably many of them would generate no observers at all. So somehow we, the particular people living on earth, are the ones lucky enough to be generated from a PRNG that had a particularly short description and seed. All the seemingly random events which created each of our lives, back to the race among the spermatozoa, were in a sense pre-ordained based on a relatively small seed for a PRNG that goes back before the big bang. There really was no other way things could happen, once we got human civilization going. That would have long since used up all of the randomness. From then on everything has been predetermined. In effect we live in a deterministic universe after all, just as much as the most rigid Newtonian clockwork. So these are the major problems that I know of with the concept of basing measure for all objects on the UDist, which then leads to Schmidhuber's multiverse. In exchange for these though we do get some interesting predictions and explanations, which I have largely posted before, but here are a few of them repeated: 1. The physical laws of our universe should be expressible as a relatively simple computer program, and likewise with the initial conditions. 2. The universe should not be much bigger than it needs to be in order to allow human beings to exist. 3. There should be no substantially simpler computer program that can produce observers nearly as easily as our universe does. 4. There should not be vastly greater numbers of aliens in the universe than humans. 5. There should not be vastly more human beings (or anything we would consider observers) in the entire future of the universe than are alive today. 6. There should not be vastly more conscious animals in the world than humans. 7. If it ever becomes possible to miniaturize and/or greatly speed-up the human mind, we should be surprised to find ourselves as such a person (unless that number of such minds is greatly increased to compensate for these factors). 8. We will almost never find ourselves experiencing human observer-moments that have much lower measure than typical ones (such as being a one million year old cave man). I see these as very powerful predictions for such a simple model, and my hope is that the problems with the UDist will be able to be cleared up with continual improvements in our understanding of the nature of computation. Hal Finney
Re: is induction unformalizable?
One question I am uncertain about is this: how well could we test a supposed halting-problem oracle (HPO) box? In particular I wonder, suppose it turns out that P=NP and that further there is an efficient algorithm to solve any NP problem. For those unfamiliar with this terminology P means polynomial time, and we say that problems in P can be solved efficiently. NP means nondeterministic polynomial time, and essentially this means that for problems in NP, we can efficiently test a purported solution for correctness. Whether P is equal to NP or merely a subset of it is one of the major unsolved problems of computer science. But what if the aliens have solved it, and (somewhat to our surprise) the answer is that every NP problem can be efficiently solved. And they have embedded this NP solving algorithm (along with some other ones) in the HPO box. My concern is that to test the HPO box we could for example give it a problem we have solved and see if it gets the answer. But success might just imply that the HPO had substantially (but not astronomically) greater computing power than the human race can bring to bear. Or we could give it a problem we can't solve and then check the answer the HPO gives, but if the answer is testable that would mean it is in NP, and so even success in this area could be explained if P=NP as above. It is much less philosophically challenging to imagine that P=NP than to imagine that a true HPO could exist. Things would be different if we ever get a proof that P < NP but we aren't in that situation now. Are there other tests we could give, harder ones, that could give us evidence that it was a true HPO, that could not be fooled by an NP solver? My knowledge of these areas is pretty spotty. The only non NP problem I know of offhand is the travelling salesman problem, finding the shortest path visiting everyone of a set of cities with specified distances between each pair. Proposed solutions cannot be tested efficiently, as far as I know. If the box solved travelling salesmen problems for us, it might be a boon to salesmen but we would not necessarily know if we were getting truly optimal paths. So in Wei's story, when the scientists go to test the HPO box, how strong is the evidence that they can reasonably expect to get for it being a real HPO? And I suppose a practical point arises as well; even if it is not a true HPO, if it is nevertheless able to solve every problem we give it, it's probably worth the money! Hal Finney
Re: The Time Deniers
Russell Standish writes: > On Wed, Jul 13, 2005 at 04:20:27PM -0700, "Hal Finney" wrote: > >=20 > > Right, that is one of the big selling points of the Tegmark and > > Schmidhuber concept, that the Big Bang apparently can be described in > > very low-information terms. Tegmark even has a paper arguing that it > > took "zero information" to describe it (but frankly I am getting pretty > > turned off on the "zero information" concept since several people here > > use it to describe completely different things, and if it really took > > zero information then there couldn't be more than one thing described, > > could it?). > >=20 > > Tegmark does not say his model has "zero information" (at least not in > the classic 1998 paper). His words were (pg 25 of my copy): > > "In this sense, our "ultimate ensemble" of all mathematical structures > has virtually no algorithmic complexity at all." > > Note, this is not zero, but simply small (at least compared with the > observed complexity of our frog perspective). Thanks for the correction. I was actually thinking of a different Tegmark paper, http://space.mit.edu/home/tegmark/nihilo.html, but I see on closer reading that he also says there that the algorithmic information content of our universe is "close to zero" but does not actually say it is zero. > There is only one zero information object, and that is the set of all > descriptions (all infinite length bitstrings).=20 Do you really think there is such a thing as a "zero information object"? If so, why do you have to say what it is? :-) Is this just an informal concept or is there some formalization of it? Surely Chaitin's algorithmic information theory would not work; inputting a zero length program into a typical UTM would not produce the set of all infinite length bitstrings; in fact, I don't see how a TM could even create such an output from any program. Hal Finney
RE: is induction unformalizable?
e concept of object description in the language of set theory? Can you sketch how that would work? > STUM along with ASSA does a much better job of formalizing induction, but > I recently realized that it still isn't perfect. The problem is that it > still assigns zero probability to some objects that we intuitively think > is very unlikely, but not completely impossible. An example would be a > device that can decide the truth value of any set theoretic statement. A > universe that contains such a device would exist in the set theoretic > hierarchy, but would have no finite description in formal set theory, > and would be assigned a measure of 0 by STUM. > I'm not sure where this line of thought leads. Is induction > unformalizable? Have we just not found the right formalism yet? Or is > our intuition on the subject flawed? The mainstream view, I gather, is that induction is indeed unformalizable. The contrary claim, that induction can be formalized, would be considered controversial. Another way to express the problem is to think of trying to build an optimal induction machine. It could use Bayes theorem to update its beliefs, but what about the priors? Same problem. We could use the Universal Prior but it gives probability 0 to HPOs. Then there are all those other priors that implicitly assume infinite computation, so where does it stop? There are no end to infinities, and as Wei's example shows, there is apparently no place to stand once you start down that road. It would be absurd to suggest, say, that everything up to Aleph-23 has Platonic existence, while infinities from Aleph-24 on up are mere mysticism. Likewise, building a universe out of a UTM+HPO doesn't make sense because as Wei says, there is a 2nd-order HPO, an HPO2, which is beyond the scope of UTM+HPO, so what if the aliens show up with one of those? For a multiverse model to make sense it has to be simple, distinctive and (ideally) unique. We don't quite achieve uniqueness with the UDist (due to the arbitrary choice of a UTM which creates a multiplicative constant difference on measure), which is a major flaw. But adding oracles makes the problem infinitely worse. Here's what I conclude. If we really believe in the Universal Distribution, then we ascribe probability zero to HPOs. That means that in Wei's story, indeed the aliens are tricking Earth. If we try to imagine a universe where the aliens are legitimate and have real HPOs, that is impossible. We are just confusing ourselves if we think such a universe could be real. There is no point in even considering thought experiments based on it, any more than imagining what would happen if aliens showed up with a logical formula which was obviously simultaneously true and false. So given that we stand upon the UDist, there is no need to pay much attention to these kinds of thought experiments. I would suggest that evidence for or against the UDist should come more from the fields of mathematics and logic than from any empirical experience. My hope is that further study will lead to a computational model which is distinguished by its uniqueness and lack of ambiguity. That seems necessary for this kind of explanation of our existence to be successful. Hal Finney
RE: The Time Deniers
from one > location on the bitstring to another...if it's possible to define a > mathematical notion of "causal structure" for any particular algorithm, I > would think it would be possible to apply it to *all* algorithms. But > perhaps no such mathematical notion of causal structure will be > forthcoming...the reason I'd guess it is is that such a notion would seem > essential for defining what it means to "instantiate" a particular observer > in such a way that you don't count things like lookup tables, and also so > that you don't end up concluding that random thermal vibrations in a rock > actually instantiate all possible algorithms (the problem discussed in > Chalmers' paper "Does a Rock Implement Every Finite-State Automaton?" at > http://cogprints.org/226/00/199708001.html ). The model I suggested the other day, basically just the Universal Distribution, IMO fully solves these two riddles. First, the question is not "are they conscious" but "how much measure do they add to the particular observer-moments which they are putatively experiencing". And the UDist shows that this can be answered in a straightforward, quantitative way, by asking what is the shortest program that takes these data structures as input (the lookup table or the rock) and outputs something that matches our canonicalized representation of the OMs in question (perhaps a schematic representation of a neural network with specified firing patterns). I can tell you that the rock isn't going to add any measure. I don't know about the lookup table, maybe there is an algorithm to use it to deduce the neural network that would have created it. Hans Moravec argued that there was such an algorithm, at least for a big enough lookup table. But in principle it is an empirical question in the framework based on the UDist. There's nothing fuzzy or philosophical about it. > Well, that's what I was talking about in my last post when I said that my > intuition of "causal structure" is not a time-asymmetric one, that it would > only be about saying two events are causally related without specifying one > as the "cause" and the other as the "effect". And as I said, my > understanding of loop quantum gravity is that it does involve some notion of > building spacetime out of relationships between events without any > time-asymmetry being involved. Maybe so, I don't know much about LCG. > >Scerir has also posted some interesting paradoxes along these lines > >relating to QM. Suppose we have a photon that passes through a > >polarizer oriented at 20 degrees from vertical, then through one > >oriented at 40 degrees, and makes it through both. At the end we would > >say its polarization was 40 degrees. But what was it between the two > >polarizers? Conventionally we would say that the first polarizer made its > >polarization become 20 degrees and the second polarizer then changed the > >polarization to 40 degrees. But actually you can just as easily argue > >that the photon polarization was 40 degrees between the two polarizers. > >That interpretation works just as well, a sort of retroactive causality. > > What would the MWI say about this? Whatever it would say, I'm pretty sure it > wouldn't say that there was a single photon in a definite state between the > two polarizers. No, I think it does, but I might be wrong. I think it says the universe splits into two when the photon hits the first polarizer; in one the photon is absorbed and in the other the photon continues in the 20 degree polarization state. Or you can run time backwards and get the photon to be in the 40 degree state. I don't think the MWI helps much with this. Hal Finney
RE: The Time Deniers
> True, it isn't always necessary to compute things in the same order--if > you're simulating a system that obeys time-symmetric laws you can always > reverse all the time-dependent quantities (like the momentum of each > particle) in the final state and use that as an initial state for a new > simulation, and the new simulation will behave like a backwards movie of the > original simulation. One problem with this in practice is that it seems that the information needed to specify the final state is far greater than the information needed to specify the original state, at least with physics like ours. In our universe, you could take a snapshot at some time that recorded all the particle motions in a brain. Then you could evolve it forward and produce the successive subjective experiences. However, I don't think the snapshot has to be completely detailed. Some sloppiness is acceptable. The brain is robust and you could change the details of thermal motions very considerably and the brain would still work fine. If you took a snapshot at the end and evolved it backward it would also work, in theory, but in practice it would not work unless every detail of every motion was precise to an incredible degree. (This is ignoring issues of QM state reduction and such, I'm basically considering a Newtonian clockwork here.) It's like, it's easy to come up with motions to scramble an egg; but to come up with motions to unscramble one will require absolute precision in every respect. The result is that the information requirements for specifying a final-state based simulation that includes an arrow of time are exponentially greater than the information needed to create a plausible initial-state simulation. If we then add the concept of measure based inversely on the size of the information description, we find that almost all measure of such simulations comes from initial-state based ones rather than final-state based. > But since I don't have a well-defined mathematical > theory of what it means for two computations to have the same "causal > structure", I'm not sure whether the causal structure would actually be any > different if you computed a universe in reverse order. When I think of > "causal structure", I'm not really presupposing any asymmetry between > "cause" and "effect", I'm just imagining a collection of events which are > linked to each other in some way like in a graph, but the links need not > have any built-in direction--if two events are linked, that doesn't mean one > event is the cause and the other is the effect, so the pattern of links > could still be the same even if you did compute things in reverse order. > >From what I've read about loop quantum gravity, it's a theory in which space > and time emerge from a more primitive notion of linked events, but I'm > pretty sure it's not a time-asymmetric theory. My feeling is that causality, like time, is in the eye of the beholder. It's not an inherent or fundamental property. Rather, it is a way that we can interpret events in some kinds of universes. Completely chaotic universes (where every moment is random and uncorrelated with the next) would not have causality in any meaningful sense. Likewise for static universes. In fact I would suggest that causality only exists in our universe in areas where there is an arrow of time; that is, in areas which are far from equlibrium and where entropy is unusually low. The problem in equilibrium regions is that you can always look at things two ways. Suppose particle A collides with B and changes its course so that B collides with C. We can express this as that A causes B to hit C. But all the physics works just as well in the reverse direction, in equilibrium, so we could just as easily say that C caused B to hit A. Scerir has also posted some interesting paradoxes along these lines relating to QM. Suppose we have a photon that passes through a polarizer oriented at 20 degrees from vertical, then through one oriented at 40 degrees, and makes it through both. At the end we would say its polarization was 40 degrees. But what was it between the two polarizers? Conventionally we would say that the first polarizer made its polarization become 20 degrees and the second polarizer then changed the polarization to 40 degrees. But actually you can just as easily argue that the photon polarization was 40 degrees between the two polarizers. That interpretation works just as well, a sort of retroactive causality. As with time, my guess is that if we restrict our attention to observers like us, of a type we can comprehend, then automatically we are going to pick out information systems that have a notion of time, an arrow of time, and hence a sense of causality. Not all systems have these properties, but some do, and all the ones that we would identify as observers fall into that category. Hal Finney
RE: The Time Deniers
Jesse Mazer writes: > Hal Finney wrote: > >I imagine that multiple universes could exist, a la Schmidhuber's ensemble > >or Tegmark's level 4 multiverse. Time does not play a special role in > >the descriptions of these universes. > > Doesn't Schmidhuber consider only universes that are the results of > computations? Can't we consider any computation as having an intrinsic > "causal structure"? How would it be possible to write an algorithm that > describes a "Life" universe where there's no time, where the t-axis is > replaced by a z-axis, for example? Well, you could just replace the letter t with the letter z, but of course that wouldn't change the underlying nature of things. You might well say that there was still a time axis, just that it had a different name. But the bigger question is whether the order in which a universe is computed must match the concept of "time" within that universe. It is true that for universes like ours, it seems difficult to compute them in any way other than starting at the past and working our way into the future. In that case, the order of computation is the same as the within-universe time axis. However it might be dangerous to generalize and to assume that this is always the case, or that one can go so far as to define the concept of time within a universe to be the order in which things were computed. It is not difficult to come up with universes that can be computed in a different order than the "natural" within-universe direction of time. Even our own universe appears to be time-symmetric at the micro-scale. The only reason we have an arrow of time is apparently because the universe was created in a special low-entropy state. A universe without such a special state at one end could be computed in either direction. Or we could start in the middle and compute forward and backward from that point. Or maybe we could even compute it sideways, taking a particular timelike line as the "initial conditions". Further, in our own universe there appears to be quite a bit of ambiguity about time ordering, and many different computational strategies will work equally well. Relativity theory shows that events either have a timelike separation, in which case it is clear which one is in the past, or a spacelike separation, which makes it ambiguous which one is farther in the past. It was suggested here a while back that a Life universe could be computed using an algorithm which ran around somewhat randomly and made localized changes to cells in order to make them match the Life rules. Eventually this would converge to a stable and consistent Life universe. Any observers living in that universe would have a perceived direction of time that was very different from the actual order in which it was computed. However although this is possible, I think it is likely that any high-measure universe containing observers like us will pretty much have to be computed in the past-to-future direction of time. That seems to be the best way to specify a universe like ours with simple initial conditions, using a simple algorithm. So I imagine that in practice, for most universes that we are interested in, it will be correct to identify subjective (within-universe) time with computational ordering. But this is not true in general. > >Tegmark in one of his papers considers universes with two or more > >time dimensions. > > If this universe is computable, it can be simulated by an algorithm that can > run in a universe with only one time dimension. Perhaps the algorithm would > go back and forth between simulating time increments in different > directions, like how a regular computer can simulate a parallel computer. Yes, but there is still a difference between two time dimensions and one, just as there is a difference between two spatial dimensions and one. An interesting question is whether there would be any algorithms possible in a universe with two dimensional time that would run fundamentally faster than in a universe with one dimensional time. I don't understand the concept well enough to address that. But if so, a being who evolved in such a universe might deny that one dimensional time observers could exist, that such a limited notion of time would be rich enough to support the computational complexity necessary for life and intelligence to exist. Hal Finney
RE: The Time Deniers
Lee Corbin writes: > Perhaps you could address the biggest stumbling block that perhaps > I still have: continuity. > > I'll even go out on a limb and suggest that *continuity* is really > what bothers a lot of people. A lot of us (e.g. Jesse Mazer) are > quite okay with, say, a program that uses the rules of Life to > give rise to a conscious entity. But we get really squeamish when > someone talks about just using the static, instant descriptions--- > the generations of Life as depicted on, say, 2D grids. Even if you > have big a pile of such descriptions---trillions and trillions of > them---we point out that these snapshots are only frozen instants, > where the real "meat" was the continuous process (that so happened > to use the Rules). One point of my example was that if you think of the Life universe as existing in and of itself, as a Platonic entity, pure information, there is really no difference between these views. This thread talks about "time deniers" and I might be one, but from my perspective it seems that many people are "time mystics". They see a special role for time that goes beyond its mere presence as part of the laws of physics of a universe. I imagine that multiple universes could exist, a la Schmidhuber's ensemble or Tegmark's level 4 multiverse. Time does not play a special role in the descriptions of these universes. Some universes will have properties that are similar to what we think of as the passage of time; others will have nothing that would be recognizably like time; and yet others will have some aspects that are similar to time passing but not quite the same. Does a pure Life universe have a time coordinate? In a way, it does. Or you can just as easily see it as a stack of grids. Is there really a difference, if the laws of physics are the same in both cases? Alternative sets of Life rules will cause every grid in that stack to be the same, or equivalently, will cause each successive instant to have the same state. Does that universe have time? Even in the case of Life, there are other ways to create the stack of grids (or equivalently, succession of states) than to start with some initial conditions and evolve forwards. You could start with some final conditions and work your way backwards. Or you could start in the middle and work outwards. Wolfram considers computational systems (in my view, simple universes) which get defined via successive approximations in much this way. Do such universes have time? There is no unambiguous answer. Tegmark in one of his papers considers universes with two or more time dimensions. Can you wrap your mind around that? Doesn't the potential existence of such universes suggest that the notion of process vs static-state is too simple? What would a 2D-time process be like, vs a 1D-time process like what we are used to? Could we imagine universes with fractal time dimensions, like the fractal space dimensions which are sometimes explored? These considerations lead me to the view that there is nothing special about time, that it is merely a useful way of looking at some universes. Probably the fraction of universes (or more generally, information objects) that have a notion of time that is very similar to our own is small. Now, certainly it seems that consciousnesses like ours, anything that we would recognize as a conscious entity, will involve a notion of time similar to what we use. We are bound up with the idea of time and so if we see a consciousness in a Life universe, whether we think of it as a stack of cells or as a succession of states, it will seem to that consciousness that time is passing. But this is largely a selection effect of our own anthropomorphic biases. We only see consciousnesses that perceive time passing because those are the only kinds of informational entities that we can think of as conscious. > P.S. I thought UD was "Universal Dovetailer", but now you mean > "Universal Description". We've got to get cautious using the > acronyms, or be sure, as you did here, to say what you mean in > a post. Actually it is "Universal Distribution" but I didn't want to write that out in detail every time I used it. Maybe I will write UDist in the future to help remind people that no doves were harmed in creating this concept. > P.P.S. Stephen Paul King was one of those who kept bringing up > the distinction between a *description* of something and the > thing itself. With what I have written above, I see a connection > now. For an informational object, a sufficiently precise description is equivalent to the object itself, in my view. And I am considering an ontology where everything is an informational object. Hal Finney
RE: The Time Deniers
Stathis Papaioannou writes: > (c) A random string of binary code is run on a computer. There exists a > programming language which, when a program is written in this language so > that it is the same program as in (a) and (b), then compiled, the binary > code so produced is the same as this random string. I don't know what you mean by "random" in this context. If you mean a string selected at random from among all strings of a certain length, the chance that it will turn out to be the same program functionally is so low as to be not worth considering. But ignoring that, here is how I approach the more general problem of whether a given string creates or instantiates a given observer. I made a long posting on this a few weeks ago. In my opinion it follows simply from assuming the Universal Distribution (UD). In this model, all information objects are governed by this probability distribution, the UD. One way to think of it is to imagine all possible programs being run; then the fraction of programs which instantiate a given information object is that object's measure. So to solve the problem of whether your program instantiates an observer is a two step process. First write down a description of the information pattern that equals that observer. More specifically, write the description of the information pattern that defines that observer experiencing the particular moments of consciousness that you want to know if your program is instantiating. Doing this will require a much stronger and more detailed theory of conciousness than we now possess, but I don't think there is any inherent obstacle that will keep us from gaining this ability. The second step is to consider your program's output and see if it is reasonably similar to the information pattern you just defined. The simplest case is where the output is identical. Then you can say that the program does instantiate that consciousness. However it could be that the program basically creates the same pattern but it is represented somewhat differently. How can we consider all possible alternate ways of representing an information pattern and still let them count, without opening the door so wide that all patterns count? The solution follows rigorously from the definition of the UD. We append a second interpretation program to the first one, the one which ran the putative conscious program. This second program turns the output from the first one into the canonical form we used to define the conscious information pattern. The concatenation of the two programs then outputs the pattern in canonical form and we can recognize it. The key point now is that the contribution to the measure of the observer moments being simulated is, by the definition of the Universal Distribution, based on the size of the program which outputs the information pattern in question. And the size of that program will be the size of its two component parts: the first one, that you were wondering about, which may have generated a consciousness; and the second one, which took the output of the first one and turned it into the canonical form which matched the OM pattern in question. In other words, the contribution which this program makes to the measure of a given observer's experience will be based on the size of the program (smaller is better) and on the size of the interpretation program which turns the output of the first program into canonical form (again, smaller is better). Obviously a sufficiently large interpretation program can turn any output into what we want. The question is whether a small one can do the trick. That is what tells us that the pattern is really there and not something which we are forcing by our interpretation. Standard considerations of the UD imply that the exact nature of the canonical form used is immaterial, however it does matter how precisely you need to specify the information pattern that truly does represent a set of conscious observer moments. That second question is a matter of psychology and as we improve our understanding of consciousness we will have a better handle on it. Once we do, this approach will provide an in-principle technique to calculate how much contribution to measure any given program string makes to any given conscious experience. Most importantly, this follows entirely from the assumption of the Universal Distribution. No other assumptions are needed. It is a simple assumption yet it provides a very specific process and rule to answer this kind of question. Hal Finney
RE: The Time Deniers
Lee Corbin writes: > Hal Finney writes > > Can we imagine a universe like ours, which follows exactly the > > same natural laws, but where time doesn't really exist (in some > > sense), where there is no actual causality? > > You yourself have already provided the key example in imagining > a two dimensional CA where the second dimension can be taken as > y instead of t. Okay, but perhaps I wasn't quite clear. I meant this to be a two dimensional CA that was completely self-contained, a universe of its own. It is not something that is embedded in our own universe or any larger structure. It is a self-contained mathematical/physical object with its own set of natural laws, just as we imagine our own universe to be. My point was that whether we label the two dimensions x and t or x and y shouldn't make any difference in the properties of that universe. It still has the same fundamental structure. Changing the names only changes how we describe it, not what it is. So I don't see this as an example of what I described above, a universe which matches another in its "laws of physics" but where one has causality and the other does not. That is, not unless someone would claim that it makes a difference whether the 2nd dimension is named y or t. Hal Finney
UD + ASSA
this point I am trying to keep to the big picture. Objects have measure, and for that to be meaningful, objects with higher measure have to be considered more prominent. We should expect the universe we observe to have relatively high measure. We should expect ourselves as observers, and as observer moments, to have relatively high measure. If we face alternatives of either a low measure or a high measure future, we should expect to experience the high measure one. As far as the problem of "being" unconscious objects, I don't necessarily see that as contradictory. We all know what it is like to be unconscious. We become unconscious every day when we sleep. We also know through experience that there are many degrees and kinds of consciousness. In practice, being a table or the number 3 is so different from what we think of as consciousness that we cannot relate to it as human beings. We need to restrict our attention to information objects that have a similar nature and complexity to our own. Among those objects, we can distinguish between ones with low and high measure. The theory predicts that we should find ourselves as entities with a relatively high measure, and explains those aspects of our existence which have a high measure. The ASSA is well suited for this interpretation, because it relates measure of observer moments to subjective probability. The older SSA, which is observer based where the ASSA is observer-moment based, also can work reasonably well in this model for the same reason. But the details of ASSA vs ASA vs other interpretations are not of fundamental importance in my view. The most important part is the UD. We then connect its definition of measure to subjective experience using the concept that higher measure states are more likely to be experienced. This is the basic principle from which we attempt to make our predictions and explanations. Hal Finney
RE: The Time Deniers
Again travel has forced me to take an absence from this list for a while, but I think I will be home for several weeks so hopefully I will be able to catch up at last. One question I would ask with regard to the role of time is, is there something about time (and perhaps "causality") that goes over and above the equations or natural laws that control and define a given universe? Let us imagine a Cellular Automaton based universe; for simplicity, let it be a 1-dimensional CA such as those studied in detail in Wolfram's book. We have an x dimension and a t dimension, and some rules which are the "natural laws" of that universe. A sample rule might be s[x,t+1] = s[x,t] XOR (s[x-1,t] OR s[x+1],t]). This means that the state at position x and time t+1 is the exclusive-or of the state at the previous time (s[x,t]) and the OR of the left and right neighbor states. In other words, a cell reverses its state if either of its neighbors is "on". Wolfram investigates all 256 possible rules which determine a cell's next state from the previous state of the cell and its two neighbors. Some lead to surprisingly complex patterns and it is conceivable that such universes might even be complex enough to allow life and consciousness to evolve. So we have a notion of time, t, and space, x. The question is this. If we don't *call* it time, does that change things? Suppose we have a universe with 2 spatial dimensions, x and y. But it is governed by the same rule: s[x,y+1] = s[x,y] XOR (s[x-1,y] OR s[x+1],y]). Here I have replaced t in the rule above by y. Does this make a difference? I think we will agree that it does not. Changing the letter t to the letter y does not change the fundamental nature of this universe. It only changes how we describe it. Then we can ask, is this rather abstract description of the universe, in terms of its natural laws, enough for us to know whether the consciousnesses that exist in it are really conscious? Or do we need to know more? Do we need to know details about how the universe was created (whatever that means!)? Do we need to know if there is a "flow" of "causality" in this universe? My answer is that the natural laws ought to be enough. If we can find a reasonable interpretation (defined rigorously as a mapping whose information content is significantly smaller than the pattern itself) of a pattern in the universe as something that we would consider a conscious observer in our own universe, then we would be right to say that this CA universe has consciousness. (More precisely, that this CA universe contributes measure to these instances and kinds of conscious observers.) I don't think it makes sense to demand more information than the natural laws (like, what kind of universal-computer is running to interpret these laws, what algorithm it uses, how sequential is it, is it allowed to backtrack and change things, etc.). The laws themselves define the universe. The two are, in a sense, equivalent. That is all the information there is. The laws should be, in fact they must be, enough to answer the question about whether the consciousness which appears in such a universe is "real". That's how it appears to me. In our own universe, we too have natural laws that relate to space and time. One such law is from Newton: d2x/dt2 = Force/Mass (i.e. F=ma). Relativity and QM have their own laws that refer to x, y, z, and t. Generally, t is treated differently than the other coordinates, which are all treated the same. But obviously we could substitute some other letter, say q, for t and it would not make a difference. A universe with quime instead of time would be the same. So again, is it enough to look at the natural laws of our universe in order to decide whether the consciousnesses within it are real? Or do we need more? Can we imagine a universe like ours, which follows exactly the same natural laws, but where time doesn't really exist (in some sense), where there is no actual causality? I have trouble with this idea, but I'd be interested to hear from those who think that such a distinction exists. Hal Finney
Re: Duplicates Are Selves
I have been on vacation so I have a large backlog of messages to read! But they are very interesting and full of challenging ideas. I find this list to be one of the best I have ever been on in terms both of fearlessly exploring difficult areas and also remaining cordial and polite. I am trying to understand Lee Corbin's idea about duplicates as selves better. I can understand seeing exact, synchronized duplicates as selves (such as two computers running the same simulated individual in lock-step). But when they begin to diverge I understand that Lee still sees them as (in some sense) "himself" and one copy would in fact sacrifice to benefit a diverged copy just as much(?) as to benefit its own body. Is this right? What I would ask is, is there a limit to this? Is this common-self-ness a matter of degree, or is it all-or-none? Is there some degree of divergence after which a copy might be somewhat reluctant to continue to view its brother copy as being exactly equivalent to itself? For example, what if someone were an identical twin? In some sense they are duplicates at the moment of conception who then begin to diverge. This seems to be different from the copies we discuss merely in degree of divergence, not in kind. Would it be reasonable to argue that an identical twin "should" view his brother as himself? And what about the possibility of creating non-identical copies? Perhaps our copying machine is imperfect and the products are not quite the same as the original. They are very close, perhaps so close that only extremely detailed inspection can detect the differences. Or perhaps they are not really so close at all and the copies in fact bear little resemblance to their originals. How does the potential existence of such imperfect copying machines affect the notion that one should view copies as selves? If imperfect or diverged copies are to be considered as lesser-degree selves, is there an absolute rule which applies, an objective reality which governs the extent to which two different individuals are the same "self", or is it ultimately a matter of taste and opinion for the individuals involved to make the determination? Is this something that reasonable people can disagree on, or is there an objective truth about it that they should ultimately come to agreement on if they work at it long enough? Hal Finney
RE: Copies Count
Stathis Papaioannou writes: > Hal Finney writes: > >Suppose you will again be simultaneously teleported to Washington > >and Moscow. This time you will have just one copy waking up in each. > >Then you will expect 50-50 odds. But suppose that after one hour, > >the copy in Moscow gets switched to the parallel computer so it is > >running with 10 times the measure; 10 copies. And suppose that you know > >beforehand that during that high-measure time period (after one hour) > >in Moscow you will experience some event E. > > Again, it's a two step process, each time considering the next moment. > First, 50% chance of waking up in either Moscow or Washington. Second, 100% > chance of experiencing E in Moscow or 0% chance of experiencing E in > Washington. The timing is crucial, or the probabilities are completely > different. Doesn't this approach run into problems if we start reducing the time interval before the extra copying in Moscow? From one hour, to one second, to one millisecond? At what point does your phenomenological expectation switch over from 90% Washington to 90% Moscow? And does it do so discontinuously, or is there a point at which you are "just barely" conscious enough in Moscow before the secondary duplication, that perhaps the two probabilities balance? I am doubtful that this approach works. Jesse Mazer suggested backwards causation, that the secondary copying in Moscow would influence the perceptual expectation of waking up in Moscow even before it happens. So he would say 90% Moscow from the beginning. However I think that has problems if we allow amnesia to occur in Moscow before the amplification. I have been enjoying these discussions but unfortunately I will have to take leave, I am going on vacation with the family for a week so I will have little chance to participate during that time. I'll look forward to catching up when I return - Hal Finney
Re: another puzzzle
Stathis Papaioannou writes: > That is the basic idea behind these thought experiments with copies: as a > more easily understood analogy for what happens in the multiverse/plenitude. I don't agree, and in fact I think the use of copies as an analog for what happens in the multiverse is fundamentally misleading. If it were not, you could create the same thought experiments just by talking about flipping coins and such. What is the analog, in the multiverse, of pushing a button to make a copy? When faced with the chance of torture, you are going to push a button to make a copy. What does that correspond to in the multiverse? The closest I can suggest is flipping a coin such that you don't get tortured if it comes up heads. Well, that destroys the whole point of the thought experiment, doesn't it? Of course you'll flip the coin. Anyone would. Pushing a button to make a copy is completely different. That's why we have so much disagreement about what to do in that case, while there would be no disagreement about what to do if you could flip a coin to avoid being tortured. That in itself should be a give-away that the situations are not as analogous as some are suggesting. I would suggest going back over these thought experiments and substitute flipping coins for making copies, and see if the paradoxes don't go away. I believe that many of the paradoxes in the copy experiments are because people do not grasp the full meaning of what copying implies. They are thinking very much in the lines Stathis suggests, that it is a variant on flipping a coin. But it's not. Copying is fundamentally different from flipping a coin, because copying increases measure while coin flipping does not. Measure is crucially important in multiverse models because it is the only foundation for whatever predictive or explanatory ability they possess. Choosing to overlook measure differences in analyzing thought experiments inevitably leads to error. Treating copying like coin flipping is just such an error. If you would instead think through the full implications of copying you would see that it is completely different from flipping a coin. The increase of measure that occurs in copying manifests in the world in tangible and obvious ways. Its phenomenological consequences are no less important. These considerations must be included when analyzing thought experiments involving copies, otherwise you are led into paradox and confusion. Hal Finney
RE: Torture yet again
Jesse Mazer wrote: >Suppose there had already been a copy made, and the two of you >were sitting side-by-side, with the torturer giving you the >following options: >A. He will flip a coin, and one of you two will get tortured >B. He points to you and says "I'm definitely going to torture >the guy sitting there, but while I'm sharpening my knives he >can press a button that makes additional copies of him as many >times as he can." >Would this change your decision in any way? What if you are >the copy in this scenario, with a clear memory of having been >the "original" earlier but then pressing a button and finding >yourself suddenly standing in the copying chamber--would that >make you more likely to choose B? I think this variation points to the major flaw in this thought experiment, which is the implicit assumption that copying is possible yet is not used. In fact, if copying is possible as the thought experiment stipulates, it would tend to be widely used. The world would be full of people who are copies. You would be likely to be an nth-generation copy. There would be no novelty as Jesse's variation suggests in allowing you to experience (presumably for the first time!) being copied. I keep harping on this because copying increases measure. It is different from flipping a coin, which does not increase measure. Your expectations going into a copy are different. To the extent that this language makes sense, I would say that you have a 100% chance of becoming the copy and a 100% chance of remaining the original. This is different from flipping a coin. You may think that it would feel the same way, but you've never tried it. Fundamentally, our perception of the world, our phenomenology, our sense of identity and our concept of future and past selves are not intrinsic, but are useful tools which have *evolved* to allow our minds to achieve the goals of survival and reproduction. In a world where copying is possible, we would evolve different ways of perceiving the world. I believe that in such a world, we would perceive the aftermath of copying very differently than the aftermath of flipping a coin. The effects are different, the evolutionary and survival implications are different. In the world of this thought experiment, if the additional copies are (via special dispensation) going to be treated well and given a good chance to survive and thrive, then yes, most people would press the button like crazy. It's just like today, if a bachelor were given the opportunity to have sex with a dozen beautiful women, he'd jump at the chance. It's not because of any intrinsic value in the act, it's because evolution has programmed him to take this opportunity to increase the measure of his genes. In the same way, pressing the button would increase the measure of your mind, and it would be equally as rewarding. In the spirit of this list, let me offer my own variation. It is like the original, except instead of torture you are offered a 50-50 chance to experience a delicious meal prepared by an expert chef. Or you can press the button to make some copies, in which case you get a 100% chance of having the meal. For me, pressing the button is a win-win situation, assuming the copies will be OK. I certainly don't think that pressing the button reduces the measure of my enjoyment of the food. Hal Finney
Re: Measure, Doomsday argument
Quentin Anciaux writes: > Why aren't we blind ? :-) > > If the "measure" of an OM come from the information complexity of it, it > seems > that an OM of a blind person need less information content because there is > no complex description of the outside world available to the blind observer. > So as they are less complex, they must have an higher "measure" ... but I'm > not blind, so as a lot of people on earth... There may be something of a puzzle there... Although I think specifically that blind people don't necessarily have a lower information content in their mental states. It is said that blind people have their other sense become more acute to take over the unused brain capacity (at least people blind from birth). So their mental states may take just as much information as sighted people. Beyond that, the puzzle remains as to why we are as complex as we are, why we are not simpler beings. It would seem that one could imagine conscious beings who would count as observers, as people we "might have been", but who would have simpler minds and senses than ours. Certainly the higher animals show signs of consciousness, and their brains are generally smaller than humans, especially the cortex, hence probably with lower information content. Of course there are a lot more people than other reasonably large-brained animals, so perhaps our sheer numbers cancel any penalty due to our larger and more-complex brains. Hal Finney
Re: Torture yet again
Jonathan Colvin writes: > You are sitting in a room, with a not very nice man. > > He gives you two options. > > 1) He'll toss a coin. Heads he tortures you, tails he doesn't. > > 2) He's going to start torturing you a minute from now. In the meantime, he > shows you a button. If you press it, you will get scanned, and a copy of you > will be created in a distant town. You've got a minute to press that button > as often as you can, and then you are getting tortured. I understand that you are trying to challenge this notion of "subjective probability" with copies. I agree that it is problematic. IMO it is different to make a copy than to flip a coin - different operationally, and different philosophically. What you need to do is to back down from subjective probabilities and just ask it like this: which do you like better, a universe where there is one of you who has a 50-50 chance of being tortured; or a universe where there are a whole lot of you and one of them will be tortured? Try not to think about which one "you" will be. You will be all of them. Think instead about the longer term: which universe will best serve your needs and desires? There is an inherent inconsistency in this kind of thought experiment if it implicitly assumes that copying technology is cheap, easy and widely available, and that copies have good lives. If that were the case, everyone would use it until there were so many copies that these properties would no longer be true. It is important in such experiments to set up the social background in which the copies will exist. What will their lives be like, good or bad? If copies have good lives, then copying is normally unavailable. In that case, the chance to make copies in this experiment may be a once-in-a-lifetime opportunity. That might well make you be willing to accept torture of a person you view as a future self, in exchange for the opportunity to so greatly increase your measure. OTOH if copying is common and most people don't do it because the future copies will be penniless and starve to death, then making copies in this experiment is of little value and you would not accept the greater chance of torture. This analysis is all based on the assumption that copies increase measure, and that in such a world, observers will be trained that increasing measure is good, just as our genes quickly learned that lesson in a world where they can be copied. Hal Finney
Re: death
Bruno Marchal writes: > Le 20-juin-05, =E0 18:16, Hal Finney a =E9crit : > > That's true, from the pure OM perspective "death" doesn't make sense > > because OMs are timeless. I was trying to phrase things in terms of > > the observer model in my reply to Stathis. An OM wants to preserve > > the measure of the observer that it is part of, due to the effects of > > evolution. Decreases in that measure would be the meaning of death, > > in the context of the multiverse. > > I will keep reading your posts hoping to make sense of it. Still I was=20= > about asking you if you were assuming the "multiverse context" or if=20 > you were hoping to extract (like me) the multiverse itself from the=20 > OMs. In which case, the current answer seems still rather hard to=20 > follow. I was trying to use Stathis' terminology when I wrote about the probability of dying. Actually I am now trying to use the ASSA and I don't have a very good idea about what it means to specify a subjective next moment. I think ultimately it is up to each OM as to what it views as its predecessor moments, and perhaps which ones it might like to consider its successor moments. Among the problems: substantial, short-term mental changes might be so great that the past OM would not consider the future OM to be the same person. This sometimes even happens with our biological bodies. I can easily create thought experiments that bend the connections beyond the breaking poing. There appears to be no bright line between the degree to which a past and future OM can be said to be the same person, even if we could query the OM's in question. Another problem: increases in measure from a past OM to a future OM. We can deal with decreases in measure by the traditional method of expected probability. But increases in measure appear to require probability > 1. That doesn't make sense, again causing me to question the whole idea of a subjective probability distribution over possible next moments. > Then in another post you just say: > > > It's a bit hard for me to come up with a satisfactory answer to this=20= > > problem, because I don't start from the assumption of a physical=20 > > universe at all--like Bruno, I'm trying to start from a measure on=20 > > observer-moments and hope that somehow the appearance of a physical=20 > > universe can be recovered from the subjective probabilities=20 > > experienced by observers Actually I didn't write this, Jesse Mazer did. But I do largely agree with this approach, and I wrote the reply: I have a similar perspective. However I think it will turn out that the simplest mathematical description of an observer-moment will involve a Big Bang. That is, describe a universe, describe natural laws, and let the OM evolve. This is the foundation for saying that the universe is real. > And this answers the question. I am glad of your interest in the=20 > possibility to explain the universe from OMs, but then, as I said I=20 > don't understand how an OM could change its measure. What is clear for=20= > me is that an OM (or preferably a 1-person, an OM being some piece of=20 > the 1-person) can change its *relative* measure (by decision, choice,=20 > will, etc.) of its possible next OMs. The OM can change the universe, and this will include changing the measure of many people's future OMs. Wei Dai, in whose footsteps I largely travel, finally decided that *any* philosophy for an OM was acceptable, and its only task was to optimize the multiverse to suit its preferences. This does not require that we introduce a subjective probability for measure of next OM, but it can allow OMs to think that way. If the current OM has an interest in certain OMs, the ones it chooses to call its "next OMs", and it wants to adjust the relative measure of those OMs to suit its tastes, that can be accommodated in this very general model. Hal Finney