On 9 May 2017 6:16 a.m., "Bruce Kellett" <[email protected]> wrote:
On 9/05/2017 1:57 am, David Nyman wrote: On 8 May 2017 8:21 a.m., "Bruce Kellett" < <[email protected]> [email protected]> wrote: On 8/05/2017 4:53 pm, David Nyman wrote: > Both Hoyle's pigeon holes and Barbour's time capsules assume that there is > a coherent underlying physics with regular exceptionless laws. Until you > have something like that, you cannot define consistent continuations. > > But I'm afraid that's implied by assumption unless one takes the view that > the evolution of physical states is fundamentally incomputable, > But I thought that that was what Bruno claimed. If one assumes physics in one's derivation, then the circularity is vicious. Oh dear no, that's not right at all. What is uncomputable is any extrinsically conceived *extraction* of physics from the computational Babel consequent on the theory. There is no possible search function for this. That extraction then is necessarily a complex consequence of observer selection. Post such extraction, the evolution of physical states is then by assumption finitely computable, modulo the FPI, else computationalism must fail as a theory of mind or of physics. At this point the objective situation, mutatis mutandis, is essentially equivalent to Everett's relative state assumptions. The other point on which I must take you to task is again the question of circularity. It's not the job of computationalism's toy model to explicate every detail of the extraction of physics, although it's already the case that it *predicts* the multiple continuations implicit in the wavefunction, which is more than can be said for QM itself which merely retrodicts them (again modulo the FPI). Given the conjunction of the assumption of computationalism and our observation of the physical environment described by QM, all the theory has to show at this stage is that it is not incompatible with these data (as it would be if, say, the evolution of the wavefunction itself were shown to be uncomputable). It should further explicate some reasonably convincing justification for why just such a physics might be expected to underpin the effective environment we observe. But the *facts* of our observation of such a physics are not at issue. There is no relevant question of circularity to deal with here. As to the so called Occam catastrophe, as exemplified in your Boltzmann brain scenario, potential resolution necessarily can be understood under computationalism only from a first person perspective, as I previously suggested to you. We need to justify, in terms of a subjective measure, why we should indeed expect the physics we observe to emerge as the predominating computational mechanism underlying our normally intelligible perceptions. To do this we only need to show that "last Tuesday" computational snippets can only reinforce, and magical or unintelligible ones cannot interfere, with "normally intelligible" and complexly connected continuations. A way to grasp this intuitively is in terms of something like Hoyle's "amnesic multiple personality" heuristic which, though as you say it was originally based on the assumption of physics, IMO illustrates the relevant considerations equally intuitively on computational assumptions. In any case, the analogy of a multitasking OS that I also mentioned suffices equally well in this regard. >From this perspective, no amount of white noise in continuations of "Boltzmann" computations could make a substantive subjective difference. The reason being that the consequence is overwhelmingly likely to be a total subjective unintelligibility which will plausibly tend to be utterly swamped, in the struggle of forgetting and remembering, by "normally intelligible" continuations. The FPI is, obviously, the relevant consideration in this regard. This is what I meant when I said that an absence of evidence for this sort of pathology or unintelligibility is not evidence of its absence. It suffices that these out of phase components of experience be swamped in the battle for what one might term personal subjective emergence. They just typically get forgotten far more frequently than they get remembered by Hoyle's multiply solipsistic agent. Hence what we may think of as pathological scenarios would be expected to be very poor and haphazard candidates in the ongoing struggle for apparently persistent, pervasive and lawful subjective emergence. What would emerge with these characteristics would then be consistently remembered histories underpinned by a robust and reiterative physical mechanism whose highly selective observation by us would then be the final evidence of its predomination in this epic personal struggle. I gave you an illustration a few days ago (on which you didn't comment) of what one might term the "psycho-theological" aspect of computationalism. I said that consciousness or first person subjectivity was really a pointless cherry on the cake of physics whose mechanism must be assumed to proceed without any a priori need of such a baroque supernumerary assumption. Indeed it can only be an a posteriori datum tacked on to the physical scheme of things. Computationalism, by contrast, can only be understood in the final analysis as a synthesis of all possible subjective personal histories. "Point of view" is then just what prevents them from all happening at once. Thus physics, under the same assumptions, can in turn be understood finally as the successful computational generator underlying the "dreams of the machines". David I find most of what you say here very much a matter of wishful thinking, and not entirely consistent at that. Let me come at it in a different way. I find Barbour's idea of time capsules quite helpful here. Each time capsule is a self-contained conscious moment. There is no progression necessarily involved, so the computation that gives one conscious moment is complete in itself, and independent of other such conscious moments. (In Barbour's picture, these moments are points in configuration space that are related physically, but we do not use that aspect here.) In the moment, you are self-aware, and aware of memories that give you a concept of self. But in that moment there is no way that you can know whether these memories are veridicial or not -- they could well all be completely false, in which case there is no "you" that continues through time as a related series of experiences. Each experienced moment is complete in itself, and there is no continuation. If all you have is the moment of consciousness, you can go no further than this. It is all an illusion, and there is no physics to extract. Of course, this is a solipsistic conclusion, but there is nothing in our experience of consciousness that shows solipsism to be false. The "I" is the "I" of the moment, nothing more. Now consider the UD in arithmetic. It dovetails all possible programs -- does all possible computations -- but most computations have nothing to do with consciousness. If we use Boltzmann's thermodynamics as an illustration of the situation, the computations of the dovetailer represent a state of thermal equilibrium, a state of maximum entropy. The characteristic of thermal equilibrium is that every microstate is equally likely -- a state of complete chaos. Similarly, in the dovetailer, every computation is equally likely and there is no order whatsoever. Occasionally, in Boltzmann's thermal equilibrium there are fluctuations to states of lower entropy in which some order emerges, but according to the second law of thermodynamics, these always return to equilibrium. Similarly, in the computations of the dovetailer, there are occasionally computations that make some sort of internal sense. Some of these correspond to conscious moments. But, as in the thermal case, these rapidly return to meaningless noise. Small fluctuations to momentary order are overwhelmingly more likely than larger fluctuations to order that persists over time -- or computations that correspond to an extended sequence of (consistent) conscious states. In fact, within the dovetailer there are undoubtedly sequences of computations that correspond to the entire history of the observable universe, from the big bang through to the final heat death. But such calculations are of measure zero in the overall picture. So, if one is to take the statistics of computations that pass through one's instantaneous conscious state in order to extract meaningful physics, one will find that the overwhelming majority of these computations are of short-lived conscious moments that rapidly return to meaningless chaos, nothing more. The dovetailer would then say that no consistent physics can ever be extracted from the statistics over conscious moments, because these statistics are dominated by chaotic continuations. That does not necessarily mean that no consistent physics exists -- as I said, all of physics will be in the computations of the dovetailer somewhere. All it means is that such physics cannot be extracted by considering individual conscious moments as primary. Physics has to have an independent existence, or it has no existence at all, and solipsism is the only answer. Thanks for your interesting comments Bruce. It's difficult to know how to respond because I still feel we are somehow at cross purposes. Perhaps I should start by commenting on the matter of wishful thinking. As I said to Brent, I don't see myself as an apologist for computationalism. Rather I'm trying to understand its possible implications. My views on the matter have changed over the years, particularly as a result of discussion on this forum, and I am perhaps more persuaded than I was originally (which is to say not at all). But I don't believe my wishes are really part of the picture. It's rather that I deliberately allow myself a modicum of intuitive latitude in these discussions - one might say going just a bit further than confidence in my position would allow in less speculative topics - mainly in order to stimulate the broadest possible critique from a valuable community of varied expertise. The thing that changed my view the most, in direct contrast to what you say above, was considering the matter from a first personal perspective rather than the traditional "view from nowhere". By this I don't mean that I believe consciousness to be more "fundamental" than physics, but rather that I began to see Bruno's point that physics would have to be a subjectively driven filtration from the computational Babel if computationalism as a whole were to make any sense. The alphabetical Babel is a useless chaos because of the impossibility of an extrinsic search function but the possibility of intrinsic self-selection via subjectivity seems like a more promising proposition. But of course this demands a fundamental theory of subjectivity and it is indeed a fresh approach to this vexing question that Bruno has brought to the party. I suspect the amount and occasional ferocity of focus on his approach stems from something more than the mere desire to prove him wrong. All that said, the point where I feel we're talking past each other is precisely on the issue of the extraction of physics. As I tried to point out, the facts of the matter are not what is at issue here. Rather the question hinges on whether it is reasonable to suppose, against the assumed background of UD*, that the vast majority of conscious moments would be a consequence of their supervening computationally on the observed physical environment rather than on random fluctuations. And the reason I make use of Hoyle's or Barbour's analogies is that they seem to lead naturally to a form of solipsism that I've called the amnesic multiple personality. Hoyle himself points this out. And far from seeing this as terminal for the argument (although frankly it amuses me that this despised philosophical position might be thus rehabilitated) I find it genuinely enlightening on the question of how to reconcile probability in a quasi-frequentist framework in an overall context in which "everything happens" with certainty. This is where what I've called the struggle or battle between remembering and forgetting comes to the fore. Admittedly it's an unfamiliar idea and hardly easy to come to terms with, not least for me, but in struggling with it I've found it genuinely enlightening with respect to many otherwise intractable puzzles, not least to do with personal identity and its putative history. In terms of our discussion, the area of disagreement which most puzzles me is why you take the view that the experience of a unique agent such as the one analogised by Hoyle or Barbour would be dominated by random events rather than the order imposed by the predominance of a robust physical-computational mechanism. I don't see why a mechanism "singularised" or selected in this manner would *at that point* fail to possess the necessary "independence" in the sense you demand of it. After all, this seems little different in effect from the so called anthropic selection invoked in other frameworks. I'm probably being a bit slow here, but could you explain again why you take this view, preferably putting it in the context of the approach I describe above if at all possible. As I said to Brent, a counter-argument is more enlightening than one that is merely different. David Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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