X-Message-Number: 4310
Date: Thu, 27 Apr 1995 22:31:38 -0700
From: John K Clark <>
Subject: SCI.CRYONICS Definitions,Computers and Beyond

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Message #4303  (Thomas Donaldson) Wrote:
       
		>I note that he does not actually give a definition 
		>[of a computer] or refer to one. 
		 
Actually I did, I said a computer was a deterministic Turing machine. 
I also said that it was a broad definition so if you want to use 
a narrower one it's fine by me.

If you accept my definition that would mean that neural nets are
computers but quantum "computers" are probably are not.  Richard
Feynman and David Deutsch did some early work on this. Seth
Lloyd published in the most respected scientific journal in the
country a design for a quantum computer, although some still say
it won't work, see  the September 17  1993 issue of Science 
page 1569  " A Potentially Realizable Quantum Computer" by Seth
Lloyd. Our own Charles Platt has written a popular account of
Lloyd's work in the March issue of Wired magazine.

Very recently  Peter Shore of Bell Labs proved that IF a quantum
"computer " is possible and could  be built, it could factor
numbers in polynomial time. A deterministic Turing Machine might
be able to do the same thing if given the proper algorithm, but
such an algorithm has not been found and most think it never will be. 
	   
Roger Penrose thinks that electrons in the micro tubules of
brain cells are doing quantum calculations, but few share his 
opinion. There is no question that as a mathematician and
physicist Penrose is absolutely world class, but most biologists
think he's a crackpot who shouldn't be poaching in their domain.
Personally I doubt if he's correct, but he's certainly no
crackpot. Interestingly he finds his most sympathetic audience
among computer designers. 
	   
		>I think that some further definitions might sharpen my
		>question. My main problem with thinking of neural nets as            
		>computers comes from the fact that they aren't programmed 
		>in any traditional sense. There is no special loading
		>of any sequence of directions to which the machine will 
		>respond.  Instead they are TRAINED: 
		 
**WARNING THE FOLLOWING IS PURE SPECULATION** If we're more like
neural net style computers than Von Neuman style computers, as
seems likely, perhaps that could explain why we have such
difficulty coming up with formal definitions, and in fact seldom
need them in everyday life, not even for very familiar concepts.
As you have said a neural net does not have a stored program in
the usual sense of the word, it's trained, that may be why I can
point to red objects but can not give a definition (a program?)
of red. The concept of "red" is still meaningful to me even
though it lacks a definition, the same is true for  "intelligence" 
and "consciousness".


			    John K Clark                  

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