From newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!bronze!chalmers Sun Dec  1 13:06:39 EST 1991
Article 1753 of comp.ai.philosophy:
Newsgroups: comp.ai.philosophy
Path: newshub.ccs.yorku.ca!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!bronze!chalmers
>From: chalmers@bronze.ucs.indiana.edu (David Chalmers)
Subject: Re: Dennett on Edelman--what a total loss
Message-ID: <1991Nov29.195200.8911@bronze.ucs.indiana.edu>
Organization: Indiana University
References: <5743@skye.ed.ac.uk> <1991Nov29.040039.19327@bronze.ucs.indiana.edu> <5757@skye.ed.ac.uk>
Date: Fri, 29 Nov 91 19:52:00 GMT
Lines: 37

In article <5757@skye.ed.ac.uk> jeff@aiai.UUCP (Jeff Dalton) writes:
>In article <1991Nov29.040039.19327@bronze.ucs.indiana.edu> chalmers@bronze.ucs.indiana.edu (David Chalmers) writes:

>>Indeed.  I agree with this claim myself.  But it this is a very
>>different claim from the claim that "the brain is a Turing Machine".
>
>Actually, it's pretty similar.  No one claims the brain is
>literally a TM, that it has a tape for example.

On the other hand, some AI opponents have been very concerned to refute
the claim.  e.g. see Edelman, TRP p. 29:

  An analysis of the evolution, development, and structure of brains
  makes it highly unlikely that they could be Turing Machines.  This
  is so because of the enormous individual variation in structure that
  brains possess at a variety of organizational levels.  A simple
  calculation shows that the genome of a human being is insuffucient
  to specify explicitly the synaptic structure of the developing
  brain.  An examination of the means by which each brain develops
  indicates that each brain is highly variable.  Moreover, each
  organisms behavior is biologically individual and enormously 
  diverse, whether or not that organism can register or report
  subjective experiences. ... An analysis of both ecological and
  environmental variation, and of the categorization procedures of
  animals and humans, makes it highly unlikely that the world
  (physical and social) can function as a tape for a Turing Machine.

This seems to be much more concerned with refuting the literal claim
than the "relevant properties can be captured by" claim.  It
seems utterly irrelevant to the weaker claim.  (Actually, I don't
really see how the appeal to individual variation is relevant to
*either* claim, but let that pass for now.)

-- 
Dave Chalmers                            (dave@cogsci.indiana.edu)      
Center for Research on Concepts and Cognition, Indiana University.
"It is not the least charm of a theory that it is refutable."


