On 22 Sep 2011, at 20:01, meekerdb wrote:

On 9/22/2011 10:02 AM, Bruno Marchal wrote:

I think what Bruno calls the 323 principle is questionable.

Can I deduce from this that UDA1-7 is understood. This shows already that either the universe is "little" or physics is (already) a branch of computer science (even if there is a physical universe).

It doesn't comport with QM. Bruno gets around this by noting that computationally a classical computer can emulate a quantum system. But I think that assumes an *isolated* quantum system.


Because the quantum entanglement is in principle unbounded and so it would take an infinite classical computer to emulate exactly.

That would only make the comp level *very* low, unless the physical universe is infinite from the start, and "I" (my 3-I, my body) is that "universe". A tiny classical universal machine, in a steady growing universe can emulate a quantum big-bang+expansion, as the UD does infinitely often.

In practice we are always satisfied with good approximations. The Hilbert space has N dimensions representing the configurations we calculate. We don't include an N+1st dimension to include "something else happens"; but it is implicitly there.

All real quantum systems big enough to be quasi-classical systems are impossible to isolate.

But then you have to assume that your brain is some infinite quantum system (but then comp is false).

Maybe not infinite but arbitrarily entangled with part of the universe which is finite but expanding.

See above.

So I'm afraid this pushes the substitution level all the way down.

Yes, I'm afraid that will be the case.

I tend to look at that as a reductio; but I'm not sure where the error is. I think it is in not allowing that one need only *approximate* the function of the brain module the doctor replaces.

But this plead for comp.

But the idea of digital approximation is fuzzy. The digital computation itself has no fuzz.

I am not sure I understand. Comp implies always a choice for some truncation. Once done, it has indeed no fuzz, and that is enough to chose a classical level of description of "my body", for which the 323- principle will be applicable. It seems to me.



If it's all the way down, then as Craig notes, there's really no difference between emulation and duplication.

But then you are, like Craig, assuming that mechanism is false. This is my point, if we want primitive matter, comp is false. (or comp implies no primitive matter, or the falsity of physicalism).




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