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From: hamscher@HT.AI.MIT.EDU (Walter Hamscher)
Newsgroups: comp.ai.digest
Subject: Natural Kinds (Re: AIList Digest   V5 #186)
Message-ID: <8707271345.AA26419@ht.ai.mit.edu>
Date: Mon, 27-Jul-87 09:45:19 EDT
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Posted: Mon Jul 27 09:45:19 1987
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Your functional description of "chair" does capture more of "what's
essential to chairs" than the structural description could.  Some
quibbles, however.  First, it includes couches since it doesn't say
that it's for exactly one person.  Second, it doesn't seem to include
"Balenz" chairs, those kind in which the person rests on his/her
shins, since the "support for one's back" is rather indirect -- what
they do is to make it easier to balance the spine by tilting the
pelvis forward.  Third, some people might say that Balenz chairs
aren't chairs at all, but stools, because the back support is indirect
-- the point being that the functional description might have to take
into account who's saying what about chairs to whom.  Probably, other
Ailist readers will come up with more borderline cases, which brings
me to the speculation that functional descriptions may end up with as
many exceptions as structural descriptions do.