Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!lll-lcc!ames!ucbcad!ucbvax!NRL-CSS.ARPA!mclean From: mclean@NRL-CSS.ARPA (John McLean) Newsgroups: comp.ai.digest Subject: Natural Kinds Message-ID: <8707161942.AA13065@nrl-css.ARPA> Date: Thu, 16-Jul-87 15:42:11 EDT Article-I.D.: nrl-css.8707161942.AA13065 Posted: Thu Jul 16 15:42:11 1987 Date-Received: Sat, 18-Jul-87 11:36:32 EDT Sender: daemon@ucbvax.BERKELEY.EDU Distribution: world Organization: The ARPA Internet Lines: 20 Approved: ailist@stripe.sri.com Even "recent" philosophical discussions of natural kinds go back 20 years and much further if you count Nelson Goodman's stuff on projectibility of predicates (why do we assume emeralds are green and not grue, i. e., green until the year 2000 and then blue?) or much of the stuff written in response to Hempel's problem whether a nonblack nonraven could could count as a confirming instance of the claim that all ravens are black (since the claim that all P's are Q's is logically equivalent to the claim that all nonQ's are nonP's). But I think you can also view much of what Plato had to say about forms and what Aristotle had to say about substance as being concerned with the problem of natural kinds as well. However, I think the issue being raised about recognizing penguins, chairs, etc. goes back to Wittgenstein's _Philosophical_Investigations_: For if you look at them you will not see something that is common to all, but similarities, relationships, and whole series of them at that...I can think of no better expression to characterize these similarities than "family resemblance"... John McLean