On 23 Dec 2011, at 21:06, meekerdb wrote:

On 12/23/2011 2:17 AM, Bruno Marchal wrote:
Why? Turing emulability of the physics that supervened on is surely irrelevant.

Unless it plays a role at some level, like you suggest by attributing a physical activity to something which is not used in a branch, but might be used in another branch, for physical reason. In that case, *such* physical acitvity is relevant, and has to be taken into account in the artificial brain, as it will be in the UD.

Although we know that brain processes are approximately classical, they are not strictly classical.

Below the substitution level, perhaps. But the computation is still classical at the correct subst level, or below, and that is what matter for the reasoning to go through.

So is it Russell's hypothesis that a strictly classical brain, as in Greg Egan's "The Singleton", would obey the 323 principle, but that real brains don't?

It looks like. But with comp we would survive even if we are sent in a classical universe, once it runs the classical computation. Russell is adding something to the comp hypothesis. It presupposes that comp works only in some type of universe. Such a refutation is a bit "bibilical". It is like saying yes to the doctor because some transcendant entity (God, a universe of type X, ...) makes it possible. it is implicit in comp that we survive because the physics allow the running of a computation in its usual classical (Church- Turing-Post sense). I might need to make that explicit perhaps?



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