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From: JMC@SAIL.STANFORD.EDU (John McCarthy)
Newsgroups: comp.ai.digest
Subject: re: AIList Digest   V5 #181
Message-ID: <8707170622.AA15750@ucbvax.Berkeley.EDU>
Date: Fri, 17-Jul-87 01:07:00 EDT
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Posted: Fri Jul 17 01:07:00 1987
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[In reply to message sent Tue 14 Jul 1987 22:58-PDT.]

The distinction I had in mind between natural kind and cluster is 
the presumed existence of as yet unknown properties of a natural
kind.

When I said "doubtful cases are rare", I left myself open to misunderstanding.
I meant that in case of chairs in Timothy's experience doubtful cases
are rare.  Therefore, for a child to presume a natural kind on hearing
a word or seeing an object is advantageous, and it will also be advantageous
to built AI systems with this presumption.

Finally, a remark concerning the "symbol grounding" discussion.  My
problems with it were mainly quantitative - there was just too much
to follow.  I suspect that Stevan Harnad's capacity to follow very
long discussions is exceptional.  I would welcome a summary of the
different points of view by someone who did follow it and feels himself
sufficiently uncommitted to any single point of view.