On 3/2/07, Mitchell Porter <[EMAIL PROTECTED]> wrote:
>From: "John Ku" <[EMAIL PROTECTED]> >I actually think there is reason to think we are not living in a computer >simulation. From what I've read, inflationary cosmology seems to be very >well supported. [...] Once you admit that you (and your whole species/civilization, assuming that it was real) may have always been living in a simulation, any cosmological reasoning that was empirically supported becomes moot. "Inflationary cosmology seems to be very well supported" - here inside the simulation! That tells you nothing about the external world. This line of thought would matter only if inflationary cosmology were well-supported A PRIORI, out of all possible worlds. In other words: you are attempting to reason about the odds that we are living in a simulation. *If* the possibilities were limited to "We are embodied natural intelligences living in a Standard Model cosmology, just as we seem to be", and "We are brains-in-vats / deluded software daemons .., whose captors / makers are living in a Standard Model cosmology" - then one could makes some guesses about probable demographics across the whole of space-time in such a universe, including space colonization by post-Singularity civilizations, etc., and derive the relative odds of the two scenarios. But the possibilities are not limited in this way. I see that Nick Bostrom acknowledges this consideration in FAQ 11 at his 'simulation argument' site, and says he knows no way of estimating the probabilities if one discards the implicit assumption that real-world physics resembles that of the simulation. The attempt to treat the universe as a Turing machine, and to make one's absolute prior a distribution across all possible programs, or all possible Turing machines, or all possible programs in all possible Turing machines - that is something of an attempt to get away from the implicit restriction involved in only thinking about M-theory universes, or whatever. But it still has problems. The classic model of a Turing machine is of an infinite tape, with a programmable read-write head moving along it. If one performs one's calculations in this context, isn't one supposing that *that* is the ultimate reality - a one-dimensional chain of n-state systems, and one more complex system which takes turns interacting with them individually? Well, there are theorems in algorithmic complexity theory regarding the independence of certain results from the specific model of computation used to prove them; as I recall, along the lines of "the time complexity of algorithm X is the same in all models, except for an unknown additive constant". One might hope to carry through a generalized simulation argument in a similarly platform-independent fashion... But I think that's a false hope. Eventually, the ontological problem of locating 'observers' in such a 'universe' would have to be faced. One has to define a concept of possible world which is not just dictated by the current fashions in physics (e.g. M-theory's 'landscape'), which is not so abstract as the logical space of Wittgenstein and Lewis (any element of which is really just a set of truth values for anonymous atomic propositions, so far as I can see), and which is not so muddled as the crypto-idealist suggestions that any 'mathematical structure' or any 'program' defines a possible world.
Why that last phrase? There is a great elegance and simplicity in the idea that all mathematical structures exist necessarily, with the anthropic principle selecting out those structures with observers. There is also an inevitability to it, even if you believe that as a matter of fact there is a real physical world out there. All it takes is one infinite computer to arise in this physical world and it will generate the mathematical Plenitude. Stathis Papaioannou ----- This list is sponsored by AGIRI: http://www.agiri.org/email To unsubscribe or change your options, please go to: http://v2.listbox.com/member/?list_id=11983
