From newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!caen!garbo.ucc.umass.edu!dime!chelm.cs.umass.edu!yodaiken Sun Dec  1 13:06:35 EST 1991
Article 1745 of comp.ai.philosophy:
Path: newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!caen!garbo.ucc.umass.edu!dime!chelm.cs.umass.edu!yodaiken
>From: yodaiken@chelm.cs.umass.edu (victor yodaiken)
Newsgroups: comp.ai.philosophy
Subject: Re: Dennett on Edelman--what a total loss
Message-ID: <39963@dime.cs.umass.edu>
Date: 29 Nov 91 14:39:07 GMT
References: <1991Nov27.031545.11235@bronze.ucs.indiana.edu> <57730@netnews.upenn.edu> <1991Nov29.050859.21552@bronze.ucs.indiana.edu>
Sender: news@dime.cs.umass.edu
Organization: University of Massachusetts, Amherst
Lines: 34

In article <1991Nov29.050859.21552@bronze.ucs.indiana.edu> chalmers@bronze.ucs.indiana.edu (David Chalmers) writes:
>In article <57730@netnews.upenn.edu> weemba@libra.wistar.upenn.edu (Matthew P Wiener) writes:
>>The work of Deutsch, Landauer, Feynman, Margolus, etc has--well `shown'
>>is a bit strong, but `suggested' is a bit weak--anyway, they have
>>indicated that quantum mechanical computation is, in principal, a far
>>superior beastie, when it comes to speed, than classical Turing compu-
>>tation.
>
>This is irrelevant to the universality claim.  Of course Deutsch
>et al wanted to demonstrate the possibility of non-Turing-computable
>mechanisms, but as is well-known, they came up empty-handed.  The
>computational complexity results are interesting, but a difference
>in speed falls far short of the radical difference in power that they
>hoped for.
>

In practice, computational complexity results are a much better guide
(though far from pefect) to what can be computed, than decidability
results. There is a decision procedure for Presberger Arithmetic, but
it has not been shown that proving theorems in PreA is any easier than
proving them in PA. 

>>In short, there is good physical speculation behind the notion that
>>Church's thesis is on its way out.
>
>I don't know what "good speculation" comes to, but there's certainly
>no good evidence.  Nevertheless, I wouldn't completely dismiss the

If one could show that a physical process could only be emulated
by a computationally infeasable algorithm, then how would this be weaker
in practice, then showing that the same process was not Turing 
computable? 




