re: delayed reply

From: Marchal <marchal.domain.name.hidden>
Date: Tue Mar 9 03:59:37 1999

Gilles wrote:

>I may be wrong, but it seems to me that the notions of computer, program,
>UD ans so on... require the notion of (time ) ordering. A Turing machine is
>decribed as a sequence of states, not a set of states. But if time (as I
>think too) is an illusion, why invoke a computation instead of some static
>state? Then the set of all possible finite computations is N.
>So you are basically saying: the Universe is N. But why not R, P(R) or any
>more complicated set?

I am not really saying "the Universe is N". I am saying (loosely
speaking):

If I am N then I will see R P(R) and a lot of complicated set, including
a lot of universes and minds.

>My opinion is you are trying the same method as Descartes: believing that
>you can uncover the true reality only by thinking.

I like Descartes very much indeed. Here is one of my admittedly
provocative slogan : Descartes invented Modern Universal Science, ... and
Modern Anglo-saxon Philosophy.

> But Descartes (and his
>predecessors) failed to discover most of the physical laws. Only Galileo
>and Newton, by trying to explain experimental facts with laws, did really
>found modern Science.

Gosh!... I am afraid only a french can be so unfair to Descartes !
What about the optic laws, his pionnering work on dreams and
neurophysiology, etc. Descartes also emphasized the important role of
personal conviction in both science and philosophy ...
Without Descartes'arithmetization of geometry, neither Newton, nor
Leibnitz would have invented calculus, etc.

>It is not surprising that the people of the last XX century imagine the
>world based on a computation, just like Greeks have imagined it as a
>combination of four elements, or theologist have imagined it as driven by
>God (it confirms that consciouness can only produce ideas from the
>interaction with an outer world!)

... unless you find God in yourself ! (Take this as a pun).

But honestly I think that in the XX century there has been Church,
Turing, Post, Godel, and Kleene, which lead to theoretical computer
science.
As Godel eventually realised, Church's thesis is really a kind of
miracle: the discovery of the absoluteness of the computability concept
(and the discovery of the corresponding relativeness of the provability
concept).
I believe that it is a major result in general philosophy.
(BTW Church's thesis has nothing to do with what Deutsch call The
Church-Turing principle, unless you admit strong physicalist axiom right
at the start).

>(I agree that the world around us can be only an
>appearance, but nevertheless this appearance does exist and must be
>explained!)

I agree with you that the appearance must be explained. It is an
important point where we agree. It is exactly what I propose to do.


>So if you exhibit a property, or even an idea of which property of our
>world could eventually be found with theory of great programmer or UD or
>any theory like that, I will applaude and suscribe to the fan club.


To derive explicitely laws of nature, there is a difficulty (both my
director and Jacques Baihache have seen rather clearly) which is that I
cannot draw a clear line between the necessary and the contingent laws :
comp makes necessary to deduce (by pure thinking) only the necessary part
of physics.

Have you follow the PE-omega experience ? If yes you should understand
how comp makes it possible to predict indeterminisme, non-locality, and
even some kind of quantum logic. Obviously physicist have discovered all
that before computer scientist. But computer science is still very young,
and the idea that computer science can be "the" fundamental science is
still "in-birth" (to say the least).

But more importantly, the goal is not to derived the laws of physics by
pure thinking, the goal is to understand where does (the belief in the)
law of physics (whatever they are) comes from (much in the spirit of
Wheeler's "laws without law").

Cheers

Bruno
Received on Tue Mar 09 1999 - 03:59:37 PST