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From: rjz@JASPER.Palladian.COM.UUCP
Newsgroups: comp.ai.digest
Subject: Re: Natural kinds
Message-ID: <"870828113435.1.rjz@JASPER"@UBIK.Palladian.COM>
Date: Fri, 28-Aug-87 11:34:00 EDT
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Posted: Fri Aug 28 11:34:00 1987
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In McCarthy's message of Jul 10, he talks of the need for AI
systems to be able to learn and use "natural kinds",
meaning something like "empirically determined categorizations
of objects and phenomena in the experience of an individual".

A response by Causey (Jul 18) describes a "natural kind"
as something with "nomologically determined attributes",
and specifically distinguished this from a "functional concept"
such as a chair.

First: what is the correct definition of a "natural kind"
in philosophical usage? What precisely does it cover,
and why can't a "functional definition" define a natural kind?

Second: Sidestepping the terminological issue,
McCarthy's original point is the more crucial:
that people seem to be able to classify objects in the
absence of precise information.
This is important if individuals are to "make sense" of their world,
meaning they are able to induce any significant
generalizations about how the world works. It seems clear
that such generalizations must allow "functional definitions";
how else would we learn to recognize chairs, tables, and
other artifacts of civilization?
Perhaps we could call this expanded notion an "empirical kind".

Third: Such "kinds" are especially important for communicating with other
individuals, since communication cannot proceeed without
mutually-accepted points of
reference, just as induction cannot proceed without "natural kinds".
Being based on individual experience, no two persons' conceptions of
a given concept can be assumed to correspond
_exactly_. Yet communication is for the most part not deterred
by this. It would be a great convenience,implementation-wise,
if this meant that precise definitions of "kinds" are
unnecessary in [AI] practice.

Roland J. Zito-wolf
Palladian Software
Cambridge, Mass 02142
RJZ%JASPER@LIVE-OAK.LCS.MIT.EDU