I think I am conceiving of the dialectic in a different way from the way you are imagining it. What I think Bostrom and others are doing is arguing that if the world is as our empirical science says it is, then the anthropic principle actually yields the prediction that we are almost certainly living in a computer simulation. That is the argument I was addressing.
There is another way you can try to run the argument where you are just directly trying to argue that we are living in a computer simulation or that we can't know that we aren't because there are no a priori reasons we can marshall against it. I think this argument is much less interesting. For one thing, this argument is nothing new and has been around at least since Descartes and his idea that there could just be an evil demon deceiving us into thinking there are other minds and an external world and probably extending back to the Greek skeptics. I would concede that if the only way to know anything about the world is through purely a priori methods, then we can't trust our ordinary views about the world. But I see no reason to grant the skeptic the premise that our only means of knowing anything is through a priori arguments. We can and do know things about the world through induction and through going with the simplest theory that gives us confirmed predictions. (Somewhat of an oversimplification by the way.) The theory that the world is, say, the way inflationary cosmology says it is is simpler than the theory that our immediate observable environment is the way inflationary cosmology says it is, plus this arbitrary additional hypothesis that our immediate environment is also just a computer simulation (or for that matter, that it is this way because an evil demon wants to deceive us into thinking that or because there is an omnibenevolent, omnipotent and omniscient being that created the world to be this way, etc.). Skeptics are fond of pointing out that no noncircular argument can be given to support inductive reasoning. That is true, but a century ago, Lewis Carroll showed through his modern parable of Achilles and the Tortoise that the same holds as well for deductive reasoning. Take any deductive argument: P If P, then Q. Therefore, Q. Carroll imagines the Tortoise saying that the conclusion doesn't immediately follow. After all, someone could believe both premises and fail to see that the conclusion follows. (That had better be the case if mathematicians are to have a valuable job to do.) So, the Tortoise says, you need an additional premise: If "P" and "If P, then Q," then it follows that Q. But of course, then the Tortoise can go further and say you need yet another premise saying that if all three of those premises are true, then Q follows. And so on, ad infinitum. The lesson I take it is not that we need to be an even more extreme skeptic about deductive reasoning as well as inductive, but that it is a fundamental mistake to confuse a basic *rule of inference* like deduction or induction with another *premise* that needs to be justified. -Ku http://www.umich.edu/~jsku 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. _________________________________________________________________ Advertisement: 50% off on Xbox 360, PS and Nintendo Wii titles! http://www.play-asia.com/SOap-23-83-4lab-71-bn-49-en-84-k-40-extended.html ----- 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
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