Re: Is the universe computable?

From: Bruno Marchal <>
Date: Tue, 13 Jan 2004 12:24:07 +0100

At 16:37 12/01/04 +0100, Eugen Leitl wrote:

>If I'd kill you, you'd have no chance of thinking that thought.

Actually this is pure wishful thinking, unless you mean succeeding
to kill me and my counterparts in some absolute way, but how would
you be able to do a thing like that. I will not insist on this
startling consequence of COMP or QM, giving that you
postulate physicalism at the start. See my thesis for a proof that
physicalism is incompatible with comp. We have discuss the
immortality question a lot in this list.

>If I killed
>all animals capable of counting, "abstract immaterial numbers" would become
>exactly that: immaterial.

OK. But "immaterial" does not mean "not existing". Even a physicalist can
accept that. Only very reductionist forms of physicalism reject that.

> > Pebbles can't count themselves, obviously. But it is not because
> > pebbles can't count that two pebbles give an even number of pebbles.
> > Electron cannot solve schroedinger equation (only a physicist can do that),
> > nevertheless electron cannot not follow it (supposing QM).
>The universe does what it does, it certainly doesn't solve equations.

So we agree. (but note that anything does what it does, so what is your point).

>solve equations, when approximating what universe does. As such, QM is a fair
>approximation; it has no further reality beyond that.

That is your opinion, which is not really relevant for the question
we are talking about.

>H\psi=E\psi in absence of context is just as meaningless as 2+2=4.

I can understand that point and respect that opinion, but
what makes you so sure. Could you give me a context in
which H\psiis not equal to E\psi ? Could you give me a context in
which 2+2 is not equal to 4, and where 2, +, 4, = have their
usual standard meaning?

Perhaps we should put our hypothesis on the table. Mine is
comp by which I mean arithmetical realism, Church thesis, and
the "yes doctor" hypothesis, that is the hypothesis that there is
a level of description of myself such that I don't detect any differences
in case my parts are functionaly substituted by digitalizable device.
Do you think those postulates are inconsistent?

Received on Tue Jan 13 2004 - 06:25:28 PST

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