Bruno Marchal wrote: > Le 21-août-06, à 16:01, 1Z a écrit : > > > Exactly. And if non-phsyical systems (Plato' Heaven) don't > > implement counterfactuals, then they can't run programmes, > > and if Plato's heaven can't run programmes, it can't be running us as > > programmes. > > I would say that only non-physical system implement counterfactuals.
A counterfactual is somethingthat could have happened, but didn't. A static, immaterial systems can only handle counterfactuals by turning them into factuals -- everything that can happen does happen. It can fully capture the *conditional* structure of a programme, (unlike a "recording") at the expense of not being a process. A programme is not the same thing as a process. Computationalism refers to real, physical processes running on material computers. Proponents of the argument need to show that the causality and dynamism are inessential (that there is no relevant difference between process and programme) before you can have consciousness implemented Platonically. To exist Platonically is to exist eternally and necessarily. There is no time or changein Plato's heave. Therefore, to "gain entry", a computational mind will have to be translated from a running process into something static and acausal. One route is to replace the process with a programme. After all, the programme does specify all the possible counterfactual behaviour, and it is basically a string of 1's and 0's, and therefore a suitabale occupant of Plato's heaven. But a specification of counterfactual behaviour is not actual counterfactual behaviour. The information is the same, but they are not the same thing. No-one would believe that a brain-scan, however detailed, is conscious, so not computationalist, however ardent, is required to believe that a progamme on a disk, gathering dust on a shelf, is sentient, however good a piece of AI code it may be! Another route is "record" the actual behaviour, under some circumstances of a process, into a stream of data (ultimately, a string of numbers, and therefore soemthing already in Plato's heaven). This route loses the conditonal structure, the counterfactuals that are vital to computer programmes and therefore to computationalism. Computer programmes contain conditional (if-then) statements. A given run of the programme will in general not explore every branch. yet the unexplored branches are part of the programme. A branch of an if-then statement that is not executed on a particular run of a programme will constitute a counterfactual, a situation that could have happened but didn't. Without counterfactuals you cannot tell which programme (algorithm) a process is implementing because two algorithms could have the same execution path but different unexecuted branches. Since a "recording" is not computation as such, the computationalist need not attribute mentality to it -- it need not have a mind of its own, any more than the characters in a movie. (Another way of looking at this is via the Turing Test; a mere recording would never pass a TT since it has no condiitonal/counterfactual behaviour and therfore cannot answer unexpected questions). > That counterfactuality is the essence of (immaterial) comp. Although > here Russell has a point: the quantum multiverse seems to handle > counterfactual. Multiverse theories seek to turn the 3rd-person "X could have happened but didn't" into the 1st-person "X could have been observed by me, but wasn't". > Now if comp is correct, I cannot distinguish a > "genuine" quantum multiverse from any of its emulation in Platonia, A quantum multiverse is sitll only a tiny corner of Platonia. Physical many-world theories have resources to keep counterfactuals unobserved that immaterial MW-theories lack (including the simple of one that many mathematical possibilities do not exist physically). For instance, even if their are two informationally identical me's in different branches of a phsycial universe, it is not inevitable that any sharing or corss-over of consicousness would occur, because in a phsyical universe, cosnciousness would have something other than informational structures to supervene on. Thus me might well be able to tell that we are in a quantum multiverse rather than Platonia, on the basis that we just do not observe enough weirdness. Too broad: If I am just a mathematical structure, I should have a much wider range of experience than I do. There is a mathemtical structure corresponding to myself with all my experiences up to time T. There is a vast array of mathematical structures corresponding to other versions of me with having a huge range of experiences -- ordinary ones, like continuing to type, extraordinary ones like seeing my computer sudenly turn into bowl of petunias. All these versions of me share the memories of the "me" who is writing this, so they all identify themselves as me. Remember, that for mathematical monism it is only necessary that a possible experience has a mathematical description. This is known as the White Rabbit problem. If we think in terms of multiverse theories, we would say that there is one "me" in this universe and other "me's" in other universes,a nd they are kept out of contact with each other. The question is whether a purely mathematical scheme has enough resources to impose isolation or otherwise remove the White Rabbit problem. Too narrow: there are a number of prima-facie phenomena which a purely mathematical approach struggles to deal with. space time consciousness causality necessity/contingency Why space ? It is tempting to think that if a number of, or some other mathematical entity, occurs in a set with other numbers, that is, as it were, a "space" which is disconnected from other sets, so that a set forms a natural model of an *isolated* universe withing a multiverse, a universe which does not suffer from the White Rabbit problem. However, maths per se does not work that way. The number "2" that appears in the set of even numbers is exactly the same number "2" that appears in the list of numbers less than 10. It does not acquire any further characteristics from its context. The time issue should be obvious. Mathematics is tradionally held to deal with timeless, eternal truths. This is reflected in the metpahor of mathematical truth being discovered not found (which, in line with my criticism of Platonism, should not be taken to seriously). It could be objected that physics can model time mathematically; it can be objected right back that it does so by spatialising time, by turning it into just another dimension, in which nothing really changes, and nothing passes. Some even go so far as to insist that this model is what time "really" is, which is surely a case of mistaking the map for the territory. Consciousness is a problem for all forms of materialism and physicalism to some extent, but it is possible to discern where the problem is particularly acute. There is no great problem with the idea that matter considered as a bare substrate can have mental properities. Any inability to have mental properties would itself be a property and therefore be inconsistent with the bareness of a bare substrate. The "subjectivity" of conscious states, often treated as "inherent" boils down to a problem of communicating one's qualia -- how one feels, how things seem. Thus it is not truly inherent but depends on the means of communication being used. Feelings and seemings can be more readily communicated in artistic, poetic language, and least readily in scientific, technical language. Since the harder, more technical a science is, the more mathematical it is, the communication problem is at its most acute in a purely mathematical langauge. Thus the problem with physicalism is not its posit of matter (as a bare substrate) but its other posit, that all properties are physical. Since physics is mathematical, that amounts to the claim that all properties are mathematical (or at least mathematically describable). In making the transition from a physicalist world-view to a mathematical one, the concept of a material substrate is abandoned (although it was never a problem for consciousness) and the posit of mathematical properties becomes, which is a problem for consciousness becomes extreme. The interesting thing is that these two problems can be used to solve each other to some extent. if we allow extra-mathemtical properties into our universe, we can use them to solve the White Rabbit problem. There are two ways of doing this: We can claim either:- White Rabbit universes don't exist at all White Rabbit universes are causally separated from us (or remote in space) The first is basically a reversion to a single-universe theory (1). Mathematical monists sometimes complain that they can't see what role matter plays. One way of seeing its role is as a solution to the WR problem. For the non-Platonist, most mathematical entitites have a "merely abstract" existence. Only a subset truly, conceretely, exist. There is an extra factor that the priveleged few have. What is it ? Materiality. For the physicalist, matter is the token of existence. Maerial things, exist, immaterial ones don't. The second moves on from a Mathematical Multiverse to a physical one (3). The interesting thing about the second variety of non-just-mathematical monism is that as well as addressing the White Rabbit problem, it removes some further contingency. If the matter, physical laws, and so on, are logically possible, then the general approach of arguing for a universe/multiverse on the grounds of removing contingency must embrace them -- otherwise it would be a contingent fact that the universe/multiverse consists of nothing but mathematics. > and > the physical laws must take that into account. All forms of physics handle counterfactuals. Or do you mean it handles them in the sense of making them real -- as Deutsch insists. Multiverse theories claim that all possible worlds exist; but "possible" has more than one meaning, so there is more than one multiverse theory. Logical possibility simply means that something is not self-contradictory. Physical possibility means something is not contradictory to the laws of physics. "Five-sided square" is self-contradictory. "Water runnig uphill" is not, but it is physically impossoble. 'And, as I argued in FoR, the reality of universes in which we chose differently makes sense of (some) formally 'counter- factual' statements that don't make sense in single- universe physics, which can only help in making sense of free will. We are forced to conclude that, in spacetime physics [i.e. without a multiverse], conditional statements whose premise is false ("if Faraday had died in 1830 ...") have no meaning. '[Fabric of Reality, D Deutsch, p. 275] Suppose we agree. What is Deutsch himself to make of the counterfactuals we need to discuss the consequences of the laws of physics themselves, such as: "If charge were not conserved, the world would be a very different place"? The multiverse is no help, for by definition, it contains no worlds in which the laws are different. Deutsch's view thus implies that these essential claims about how things would have been had the laws of nature been different "have no meaning". The moral is that if we want to give truth conditions for counterfactuals in terms of possible worlds, we need the set of all ogically possible worlds, not the set of physically possible worlds. Indeed, Deutsch's whole multiverse probably counts as a single possible world in David Lewis's account, to which Deutsch later compares his own view: "The fruitfulness of the multiverse theory in contributing to the solution of long-standing philosophical problems is so great that it would be worth adopting even if there were no physical evidence for it at all. Indeed, the philosopher David Lewis, in his book On The Plurality of Worlds, has postulated the existence of a multiverse for philosophical reasons alone." [pp. 339,40], my italics. Note that it is doubtful whether the italicised counterfactual is itself meaningful, on Deutsch's view! In fact, what Lewis postulates is not a multiverse theory, in Deutsch's sense. from:- http://www.usyd.edu.au/time/price/preprints/DeutschReview-bjps.html Under David's interpretation, conditional statements whose antecedents are false in all physically possible universes, such "as there is a perpetual motion machine..." are meaningless. So are positive statements about things that don't exist in any physical universe, eg "there is a perpetual motion machine" So are negative statements about things that don't exist in any physical universe, "there is no perpetual motion machine". But, of course, we would regard the last as meaningful and true. There is in fact a whole bunch of reasons for thinking that statements don't require real-world referents to be meaningful. We judge the meanings of statements by their semantic and syntactic makeup. we don't judge them by peeping into the universe next door. We can make sense of "there is life on other planets" without knowing whether there is in fact life on other planets. If we couldn't make (linguistic, comceptual) sense of "there is life on other planets", we wouldn't know how to go about verifying its truth. The kind of linguistic/semantic meaning I have been talking about is called "sense", as opposed to reference, the real-world object a statement is about, if it is about one. The distinction originated with the Frege David's contention seems to be based on the idea that "all meaning is reference". However it is arbitrary at best. It suggests statements like "if MWI is false.." are meaningless unless there is a world where MWI is in fact false. But how can that be if there is in fact, more than one world ? --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to email@example.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 -~----------~----~----~----~------~----~------~--~---