# Re: Is the universe computable?

On Tue, Jan 13, 2004 at 12:24:07PM +0100, Bruno Marchal 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

I was referring to a gedanken experiment, of course.

> to kill me and my counterparts in some absolute way, but how would

There are several ways imaginable, I'll point you to
http://www.foresight.org/NanoRev/Ecophagy.html

I don't see how the manner of destruction of the local pocket of biological life
(which seems to be the only one in the visible universe) has anything to do
with the validity of the argument.

It's just implementation details.

> 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.

Do we have an experimental procedure to validate these fanciful scenarios?
Multiverses are nice and all; so what flavour of kool aid do you prefer?

> >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.

If you insist to label me thusly. But, really, instead of glib assertions and
pointers to your thesis (what has formal logic to do with reality?) you
are not being very convincing so far.

> >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).

My point is that formal systems are a very powerful tool with very small reach,
unfortunately.

>
>
> >People
> >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

Because we know that QM is not a TOE. You haven't heard? We don't have a TOE.
If there's such a thing as a TOE, there might be several equivalent. I would
really like to see an algorithm, showing that any TOEs are equivalent.

> >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?

This is ridiculous. You're referring to a specific notation, which needs
systems to produce and to parse. Remove all instances of such systems, and
everything is instanstly meaningless.

> 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?

I do not see how arithmetic realism (a special case of Platonic realism, is
that correct?) is an axiom. I agree with the rest of