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From: dave@cogsci.indiana.edu (David Chalmers)
Newsgroups: comp.ai,talk.philosophy.misc,sci.philosophy.tech
Subject: Re: Can Machines Think?
Message-ID: <31945@iuvax.cs.indiana.edu>
Date: 21 Dec 89 05:15:13 GMT
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Reply-To: dave@cogsci.indiana.edu (David Chalmers)
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gene edmon writes:
>...David Chalmers writes:
>>Systems with an appropriate causal structure think.
>
>Could you elaborate on this a bit? 

Well, seeing as you ask.  The basic idea is that "it's not the meat, it's
the motion."  At the bottom line, the physical substance of a cognitive
system is probably irrelevant -- what seems fundamental is the pattern of
causal interactions that is instantiated.  Reproducing the appropriate causal
pattern, according to this view, brings along with it everything that is
essential to cognition, leaving behind only the inessential.  (Incidentally,
I'm by no means arguing against the importance of the biochemical or the
neural -- just asserting that they only make a difference insofar as they
make a *functional* difference, that is, play a role in the causal dynamics
of the model.  And such a functional difference, on this view, can be
reproduced in another medium.)

And yes, of course this is begging the question.  I could present arguments
for this point of view but no doubt it would lead to great complications.
Just let's say that this view ("functionalism", though this word is a dangerous
one to sling around with its many meanings) is widely accepted, and I can't
see it being unaccepted soon.  The main reason I posted was not to argue for
this view, but to delineate the correct role of the computer and the program
in the study of mind.

The other slightly contentious premise is the one that states that computers
can capture any causal structure whatsoever.  This, I take it, is the true
import of the Church-Turing Thesis -- in fact, when I look at a Turing
Machine, I see nothing so much as a formalization of the notion of causal
system.  And this is why, in the philosophy of mind, "computationalism" is
often taken to be synonymous with "functionalism".  Personally, I am
a functionalist first, but accept computationalism because of the plausibility
of this premise.  Some people will argue against this premise, saying that
computers cannot model certain processes which are inherently "analog".  I've
never seen the slightest evidence for this, and I'm yet to see an example of
such a process.  (The multi-body problem, by the way, is not a good example --
lack of a closed-form solution does not imply the impossibility of a
computational model.)  Of course, we may need to model processes at a low,
non-superficial level, but this is not a problem.

The other option for those who argue against the computational metaphor is to
say "yes, but computation doesn't capture causal structure *in the right
way*".  (For instance, the causation is "symbolic", or it has to be
mediated by a central processor.)  I've never found much force in these
arguments.

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