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From: ISSSSM@NUSVM.BITNET (Stephen Smoliar)
Newsgroups: comp.ai
Subject: RE: UNIFIED MODEL FOR KNOWLEDGE REPRESENTATION? (IMPOSSIBLE
Message-ID: <9106120249.AA20133@lilac.berkeley.edu>
Date: 12 Jun 91 02:49:23 GMT
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In article <133090@tut.cis.ohio-state.edu> byland@iris.cis.ohio-state.edu (Tom
Bylander) writes:
>In article <9106110020.AA17886@lilac.berkeley.edu> ISSSSM@NUSVM.BITNET
>(Stephen Smoliar) writes:
>>...I question the premise that one can start with that objective
>>propositional
>>account.  This may sound solipsistic, but the only accounts we can give of
>>events of the world are based on perceptions, be they our own, those of
>>"credible sources," or interpretations of devices....
>>
>>I think it is the lack of such an objective starting point that supports
>>Cam's
>>position that the issue here is not "truth" (so, yes, Hutchison IS "barking
>>up
>>the wrong tree") but sociology--specifically the role the inter-personal
>>behavior contributes to communication....
>
>I agree that "perceptions" are not completely objective, but if they
>did not deliver some element of truth, then a lot of things become
>hard to explain.

Is a proposition having "some element of truth" sort of like a woman being "a
little bit pregnant?"  :-)
I would argue that if you want to talk about propositional accounts at all,
then you are basically buying into the rules of formal logic;  and those rules
require that a proposition be either true or false.  (Even if you choose to use
a fuzzy logic system, every USE of a proposition ultimately boils down to a
commitment to the truth or falsity of that proposition.  Making the logic fuzzy
simply allows the proposition to flip back and forth with a bit more
flexibility.)  I am further arguing that getting on in the world does
not require buying into those rules.  (To repeat Minsky's position from
THE SOCIETY OF MIND:  Logic is all right for a POST HOC systematic explanation,
but that does not mean it is any good for controlling your decision-making
behavior.)

>  How do humans and other animals with sophisticated
>sensors survive if their perceptions do not provide appropriate
>information about the world, i.e., something true about the world?

Your problem, Tom, is that you want to equate the adjectives "appropriate" and
"true."  I would argue that "true" is only a useful term in formal logic.
Outside of that realm, it has been abused to death since (at least) the days
of Pontius Pilate.  Hopefully, you will agree with me that, as far as formal
logic is concerned, truth need not have anything to do with appropriateness;
so I suggest we just chuck the term altogether and try to refine what we mean
by "appropriate."

To give you some idea of the dangers of playing with truth without the support
of formal logic, consider mirages.  Is your perception of a patch of water on
the highway on a hot day telling you "something true about the world?"  It is
certainly NOT true (even in an intuitive sense of the word) that the highway
is wet up there, as you quickly discover when you get closer.  Perhaps we have
to get even more extreme and say that we cannot talk about whether any
information about the world is "appropriate" until have we, as perceiving
agents, have subjected it to the sort of interpretation I have been discussing
in my previous articles.

>Are scientific arguments about cold fusion, ozone depletion, dinosaur
>extinction, cholesterol, and so on merely sociological?
>
An affirmative answer to this question would be sort of a REDUCTIO AD ABSURDUM
reading of Kuhn.  The funny thing is that buying into it no longer strikes me
as absurd.  There is that old joke attributed to Wittgenstein about what the
sky must have looked like before people accepted the heliocentric model.

>I think a more reasonable position is that perceptions provide
>evidence about many aspects of the world, and that the quality of our
>assertions about the world depends on the quality of the evidence that
>supports them.
>
I guess my own position is that we do not make assertions about the world while
we are behaving in it.  Therefore, it is not an issue to ask how the quality of
those assertions affect our behavior.  Rather, there is a much tighter coupling
between perception and action.  This is what Minsky is trying to get at when he
talks about "closing the loop" in THE SOCIETY OF MIND;  and it appears that
David Chalmers, Robert French, and Doug Hofstadter are trying to come with
with a concrete implementation (such is my reading of CRCC Technical Report
49 from the Center for Research on Concepts and Cognition at Indiana
University).  Logic has quite enough to do in handling that POST HOC
explanation of behavior.  Don't try to burden it with more than it can
handle!

===============================================================================

Stephen W. Smoliar
Institute of Systems Science
National University of Singapore
Heng Mui Keng Terrace, Kent Ridge
SINGAPORE 0511

BITNET:  ISSSSM@NUSVM

"He was of Lord Essex's opinion, 'rather to go an hundred miles to speak with
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