Re: (OPE-L) Re: The Church-Turing thesis

From: paul cockshott (clyder@GN.APC.ORG)
Date: Fri Jan 23 2004 - 08:09:04 EST


 Andrew:

5. Logic: formal or dialectical, and the finite/infinite distinction

It seems that we are all agreed on Godel and Chaitlin. Of course a
computer can run several things at a time so is not tied to just one
formal system. Nevertheless, however much info content you stuff
in a computer, and whatever the additional variety brought in by
consideration of initial conditions, the problem is that the universe
has a lot more 'info content' stuffed into it, than any computer.
There remains a fundamental distinction between the infinite
universe and the finite computer.
------------------------------------------
It is questionable whether the universe is strictly speaking infinite.
But your general point is valid even if we remove infinities.
The number of possible micro-configurations of systems being
computed will be greater than the number of possible configurations
of the computing system. This means that any simulation is
only approximate.

The extended form of the Church Turing thesis
given by Deutsch states that any physical system can be
simulated to an arbitrary degree of accuracy by a universal
computer, see:
Quantum theory, the Church-Turing principle and the universal quantum
computer (1985)  (
David Deutsch
Proceedings of the Royal Society of London Ser.
download from http://citeseer.ist.psu.edu/deutsch85quantum.html

Andrew:
  Ian I would be
greatful if you could give me a good reference to explain what you
mean by 'computation theory' (or whatever the correct term is). It
does seem, from my perspective, that you have a more reductionist
notion in mind than what I take from dialectics.
 -------------------

A good summary of writings in this spirit is in
'The Universal Turing Machine a Half Century Survey',
Oxford University Press.

Wolframs book 'A new Kind of Science', is also very
much in this tradition.


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