X-Message-Number: 9269 Date: Thu, 12 Mar 98 17:15:49 From: Mike Perry <> Subject: Re: CryoNet #9267 Thomas Donaldson writes, > Sorry, but the implied idea that if I don't believe we are finite Turing > machines I must therefore believe that we run by supernatural means just > doesn't ring any bells with me. If finite nonTuring machines can exist, then > that is sufficient. > Well, I haven't said that lack of belief that we are finite Turing machines *necessarily* means that "we are run by supernatural means." > Just what would be wrong, metaphysically, if the Church-Turing thesis failed? I don't see it as a necessary catastrophe. Actually, the CT thesis does not even seem necessary for my most general version of a digital argument anyway. I don't devote a lot of space in the book to defending it per se, though I do make note of it, and it too has its utility. The digital argument, more generally, which doesn't require the CT thesis but is implied by it, is useful to be able to argue a case for "unboundedness"--that all finite histories, in some sense, are real, which is an important underpinning of my book. Another important underpinning it supports is "interchangeability"--that the same person with the same experiences can occur more than once in the multiverse, which renders more credible the idea of resurrecting people by creating replicas. It is useful too for such ideas as a universal language, which I develop, and for making plausible the idea of uploading. It has a bearing on the issue of consciousness. However, I could probably soften, or retreat a bit from it if I had to (I don't see the necessity as yet). I think our *memories* are digital and don't involve anything but a finite information content, which is more important than whether our *experiences* more generally are also digital in some sense. But the digital nature of memories can be used as one more argument that *significant* experiences must be digital too! > > If by digital, you simply mean that our own experiences are discrete and > finite, I will freely admit some kind of finitude, but discreteness is > going to (at least) require more argument. I'm sure that my background, to say nothing of the space I can reasonably take up with this topic in the book, are both inadequate to really dispose of the question. But physics-trained people like Tipler and Deutsch seem to agree on what amounts to a digital paradigm as the basis of all things that happen in our reality. I have studied their arguments as carefully as I could and they seem solid enough to merit acceptance, at least on a provisional basis, which is about the best we can do with scientific arguments anyway. I am aware that many things in our experience such as vision *seem* to involve a continuum, not just discrete state changes, but I think that is a convincing illusion caused by the vast numbers of particles involved. This is certainly true of lumps of inert matter, which are made of atoms, and I think so too for events as well. As for the idea that space and time are (possibly) continuous not discrete, I answer that events don't happen at every point in spacetime but only at isolated points, when "world-lines" intersect and particles interact. On the other hand, if events are discrete but "incommensurable" it does not necessarily destroy the digital paradigm. A case in point would be a hypothetical machine that bases its behavior on the successive digits of a dimensionless, fundamental constant, assumed to be non-computable, but can only access finitely many of these digits in finite time. Again, I think the digital paradigm is well supported by modern physics, though I have to base this opinion somewhat on "hearsay" at this point. I hope in the future I can study more physics and other things and investigate this interesting question further. > as yet, general relativity and quantum mechanics remain unreconciled. As I understand it, a major source of "incompatibility" is the supposed non-locality of phenomena under quantum mechanics, which amounts to faster-than-light signaling, which is forbidden by relativity. Locality, however, is restored by the many-worlds hypothesis, which does not disturb quantum mechanics. > So think a bit: there must be some wider theory that includes the > phenomena explained by each of them, though it may disagree experimentally > with both. If we base our ideas of human survival upon either or both, > we may awaken from our suspension to find both theories, and all the > philosophies built upon them, to be history only, and dismissed by the > people of that time as we now dismiss phlogiston. This is possible, but on the other hand, there is no guarantee of it, and I think there's a good chance it won't happen, or if there is some problem, it will be remediable without throwing out the whole. Quantum mechanics looks pretty solid--as Nick Herbert says in *Quantum Reality*, it is "batting 1000"--and it is the major source I have for a "digital" argument. If it and relativity still don't jibe, even with many-worlds, I suspect relativity (with all due respect to Einstein) is what will have to give ground. So I persist. Endless best, Mike Perry Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=9269