On 14 Aug 2012, at 20:16, William R. Buckley wrote:

John:

Regardless of your dislike for the term omniscience versus universality, the Turing machine can compute all computable computations, and this simply by virtue of its construction.


It is deeper than that. It is in virtue of the fact that the set of computable functions, unlike all other sets in math, is closed for the diagonalization, and the price for this is incompleteness. It is not trivial, and makes computational universality rather exceptional and unexpected. The discovery of the universal machine is a very big discovery, of the type: it changes everything we knew. I think. For beliefs, knowledge, proofs, definability, etc. This never happens, and the corresponding formal systems can always been extended.

Bruno







wrb

From: everything-list@googlegroups.com [mailto:everything-list@googlegroups.com ] On Behalf Of John Clark
Sent: Tuesday, August 14, 2012 9:39 AM
To: everything-list@googlegroups.com
Subject: Re: Why AI is impossible

On Mon, Aug 13, 2012 at 8:09 PM, William R. Buckley <bill.buck...@gmail.com > wrote:

 > Consider that the Turing machine is computational omniscient[...]

Turing's entire reason for inventing what we now call a Turing Machine was to prove that computational omniscience is NOT possible. He rigorously proved that no Turing Machine, that is to say no computer, can determine in advance if any given computer program will eventually stop.

For example, it would be very easy to write a program to look for the first even number greater than 2 that is not the sum of two prime numbers and then stop. But will the machine ever stop? The Turing Machine doesn't know, I don't know, you don't know, nobody knows. Maybe it will stop in the next 5 seconds, maybe it will stop in 5 billion years, maybe it will never stop. If you want to know what the machine will do you just have to watch it and see, and even the machine doesn't know what it will do until it does it.

  John K Clark



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