On Wed, Oct 29, 2008 at 10:44 PM, Matt Mahoney <[EMAIL PROTECTED]> wrote: > > My assumption is that the physics of the observable universe is computable > (which is widely believed to be true).
To me, this is another topic where several different claims tangled together. [A]. "Every law or model proposed in physics is computable and therefore can be calculated by a Turing Machine." This is what Zuse argued in his original paper, which started this whole discussion. Given my limited knowledge of physics, it sounds correct, and I have no problem here. [B]. "Because of A, all laws and models in physics can be calculated by a Turing Machine." This is Zuse's hypothesis. He didn't really argue for it, but suggested it as a possibility. I think that this is theoretically possible, but practically very unlikely to happen. Physics, like any science, consists of incompatible theories each focusing on one aspect of the world. A consistent "Theory of Physics" is very hard to get, if not impossible. I don't have a high expectation for B to be realized, though do accept it as a meaningful and interesting possibility to consider, or even as an ultimate goal of research for a physicist. [C]. "Because of B, the universe can be simulated in Turing Machine". This is where I start to feel uncomfortable. Even if someone has got a theory can explains all observed physical phenomena, and formulated it in a Turing machine, it is still only a description of the universe at a certain level of description. To claim it describes "the universe", rather than just "all observed physical phenomena", you need to assume a strong version of Physicalism and Reductionism, so that all phenomena can be reduced into physical phenomena with no information loss. To me, this claim is philosophically incorrect. There is no single language or level of description that describes "the true world", while all the other descriptions are just its approximation. [D]. "Because of C, the universe is a Turing Machine". To me, this is a confusion between an object and a description/simulation of an object. Even if C is true, a simulated universe is still not a universe itself, just as a simulated hurricane in a computer is not a real hurricane itself, because it does not have the defining property of "hurricane" in our world (which is different from the simulated world in the computer). Of course, some people will go to the extreme to say that I'm really living in a simulated world, it is just that I haven't realize it yet. This is a reasonable argument, but since I don't see what difference it will make if I accept it, it won't be considered here. In summary, what I cannot accept in AGI research is the assumption that there is a real/true/object description of the universe, and all theories or knowledge are partial approximation of it. Turing Machine is just one form of this "objective truth". To me, though this opinion is acceptable in many situations in everyday life, it will lead the research of AGI to a wrong direction. Pei ------------------------------------------- agi Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/ Modify Your Subscription: https://www.listbox.com/member/?member_id=8660244&id_secret=117534816-b15a34 Powered by Listbox: http://www.listbox.com
