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Article 5387 of comp.ai.philosophy:
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>From: langston@memstvx1.memst.edu
Newsgroups: comp.ai.philosophy
Subject: Re: Physical Symbol Systems Hypothesis
Message-ID: <1992May3.221715.2048@memstvx1.memst.edu>
Date: 4 May 92 04:17:15 GMT
References: <1992May2.031108.7475@beaver.cs.washington.edu> <1992May2.190707.26464@bronze.ucs.indiana.edu>
Organization: Memphis State University
Lines: 75

In article <1992May2.190707.26464@bronze.ucs.indiana.edu>, chalmers@bronze.ucs.indiana.edu (David Chalmers) writes:
> In article <1992May2.031108.7475@beaver.cs.washington.edu> rex@cs.washington.edu (Rex Jakobovits) writes:
> 
>>I am looking for arguments against Newell & Simon's Physical Symbol
>>Systems Hypothesis (PSSH): "A physical symbol system has the necessary
>>and sufficient means for general intelligent action."  Elaine Rich
>>declares this to be the underlying assumption "at the heart of
>>research in ai".
> 
> I find the PSSH much too vague and poorly-specified to be useful.
> There are two major problems: (1) lack of clarity in what's
> meant by "symbol" and "symbol system"; (2) problems with the
> "necessary and sufficient means" clause.
> Different people construe the PSSH in either of . . . two ways, and
> it's unclear to me which one Newell and Simon meant.  Some evidence
> for the second interpretation is given by their stipulation (in
> "Computer Science as Empirical Inquiry") that a symbol must
> (a) designate, and (b) be atomic.  This is the way in which I, along
> with many connectionists, have usually construed it (so that
> one can believe in strong AI but still disbelieve PSSH).  However,
> in more recent writings Simon has taken pains to point out that
> connectionist AI is compatible with PSSH, effectively by dropping
> the requirement that symbols be atomic (so even a distributed
> representation can be a "symbol").  This actually leads to a third
> interpretation of PSSH, where there is no commitment to
> computational tokens, only to representations.

But couldn't the representations be manipulated as computational
tokens without requiring they be treated as such?


>>Can one be skeptical of the PSSH and still believe in AI?
> 
> On the strong construal, certainly -- e.g. by believing in the
> possibility of connectionist AI, or more generally in AI where
> the computational level falls below the representational level.
> On the weak construal where "symbol" = "computational token",
> maybe not.  On the weak construal where "symbol" =
> "representation", then arguably yes, e.g. if one is Rod Brooks
> or Stephen Stich, although most people find the notion of
> intelligence without representation very implausible.
> 
> -- 
> 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."

Might it be the case that the two are different sides of the same coin
(as Dave I think points out, not in so few words)?  The PSSH resides
at a purely symbolic level, whereas connectionism, subsumption, et al.
operate at a sub- or micro-symbolic level.  Examining the human brain,
and the claim that humans are PSS's, this seems to be exactly what is
meant.  The architecture is inherently subsymbolic.  However, it is
quite possible for representations and computational tokens to
emerge from this architecture.  (Right now I'm boggling at the architecture
necessary for something of this scale, but I see no reason why a
subsymbolic system could not manage computational tokens)
  The argument is basically that of pro-connectionism, with a difference.
Why throw out a theory that has had such successes?  Don't trash it
completely, just evolve it.  The 'puritans' on either side of the argument
would do well to sit back and examine the fact that they're describing two
different levels of the same activity.  It's similar to analysis of an
electrical circuit - all these electrons are rushing around at the same
time, being gated this way and that, and yet it is possible for one to
sit down and map out the circuit function linearly.  And it's quite
impossible to build the circuit without and understanding of both
levels.
-- 

Mark C. Langston                                  "What concerns me is not the
Psychology Department                              way things are, but rather
Memphis State University                           the way people think things
LANGSTON@MEMSTVX1.MEMST.EDU                        are."     -Epictetus

     "...a brighter tomorrow?!?  How about a better TODAY?"  -me


