Path: utzoo!dciem!client1!mmt
From: mmt@client1.DRETOR.UUCP (Martin Taylor)
Newsgroups: comp.ai
Subject: Re: Sci. American AI debate
Message-ID: <2818@client1.DRETOR.UUCP>
Date: 5 Jan 90 23:16:26 GMT
References: <16587@megaron.cs.arizona.edu> <6039@uhccux.uhcc.hawaii.edu>
Reply-To: mmt@client1.dciem.dnd.ca (Martin Taylor)
Organization: D.C.I.E.M., Toronto, Canada
Lines: 77


I think that what both Searle and the Churchlands (and all commentary I have
yet seen) miss is that the brain is a dynamic system whose activity in
response to an input does not stop when the "desired" output has been
produced.  There is an old saying, whose provenance I forget, about an
old man who says "Sometimes I just sits and thinks, and sometimes I just sits."
Well, Searle in the Chinese room just sits.  In dynamic terms, the
Chinese room has a zero-energy point attractor, whereas in any thinking
system the effect of a perturbation (the entry of a Chinese input) may
last indefinitely long, and may even be to shift the system from one
basin of attraction into another, so that subsequent inputs may be
interpreted completely differently.  It seems to me that the common-sense
version of "understanding" has to be based on appropriate reactions to
the intentions of the interrogator and that the things the interrogator
inputs must be affected by the output of the Chinese room.  Hence, no
account of the Chinese room can be complete if it deals with only a short
sequence of interchanges.

To put the point in everyday language, I do not believe there could be a
finite rule set that would accomodate the interchanges with a cooperative
partner, given that the partner's input comes at unpredictable moments in
the "thinking" after-effects of prior inputs.  Of course, any specific
example could be accomodated by specific rules, but imagine the set of
possibilities of the kind in which a statement from the interlocutor such
as "grass is red" might be followed by (1) "No it isn't", (2) "Oh, come on."
(3) "Yep, I'll come by on Sunday" (4) "Maybe I should phone the police"
(5) "Have another."  I can imagine situations in which each of these would
be suitable and effective responses, but I cannot imagine rule sets for
the Chinese room that could provide them in the absence of "understanding".
But the premise of the Chinese room is that such responses would be
produced in the absence of understanding.

Searle claims it to be prima facie obvious that syntax cannot give rise
to semantics.  I find this claim analogous to a claim that a set of distances
between points cannot be enough to allow one to determine the placement
of the points in an N-dimensional space.  But Roger Sheppard showed that
one can, even if one knowns only the ordering of the distances, if one
has enough distances.  Similarly I believe it would be hard to prove
that syntax cannot converge on semantics if one has enough connected
discourse with which to work.  Searle's statement that the same syntax
could be used of a chess game and of the stock market may be true for small
samples, but is unlikely to be true for large ones.  After all, unless one
wishes to be truly mystical, the structure of the input is ALL one has
to work with as a newborn infant, and from this structure (the syntax of
the environment) one determines all the meanings of the world, including
those of language.

Returning to the theme of ongoing activity:  classical symbolic programmes
usually either return the computer to its original state when they have
provided the desired output, or they move to some new state differentiated
from the original in that some memory registers have different values.
A thinking system will do more than this.  It will continue to work and
to change state.  Now there is a classical problem known as the "Halting
Problem": will a particular program halt?  A program may provably halt
(achieve a point attractor), provably not halt (achieve a limit cycle),
or not provably halt (perhaps reach a strange attractor or approach a
non-strange attractor more slowly than can be studied).  The last form
of program seems to be a candidate for a thinking system.

There is lots more behind this, but it would be labouring the point to go
into deeper detail in this forum.  Suffice it to say that I think Searle's
Chinese room has nothing to tell about the possibility of a purely
symbolic programme forming an understanding system, both because it is
not dynamic and because the rule-set cannot in principle be adequate
in the absence of dynamic continuations of performance after the prescribed
output has been produced.  The Churchlands arguments do not refute Searle,
though they do provide, in parallel systems, a mechanism that will (I think)
more readily produce real thinking systems than will a serial architecture
(recognizing that the dynamics requires responses in finite time, if
not real time).

Finally, this approach is independent of any questions about the symbol
grounding problem, on which I remain agnostic.
-- 
Martin Taylor (mmt@zorac.dciem.dnd.ca ...!uunet!dciem!mmt) (416) 635-2048
If the universe transcends formal methods, it might be interesting.
     (Steven Ryan).