Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!rutgers!ucla-cs!zen!ucbvax!OZ.AI.MIT.EDU!MINSKY From: MINSKY@OZ.AI.MIT.EDU Newsgroups: comp.ai.digest Subject: Natural Kinds (Re: AIList Digest V5 #186) Message-ID:Date: Wed, 22-Jul-87 10:43:00 EDT Article-I.D.: MIT-OZ.MINSKY.12320404487.BABYL Posted: Wed Jul 22 10:43:00 1987 Date-Received: Tue, 28-Jul-87 00:48:18 EDT References: Sender: daemon@ucbvax.BERKELEY.EDU Distribution: world Organization: The ARPA Internet Lines: 42 Approved: ailist@stripe.sri.com About natural kinds. In "The Society of Mind", pp123-129, I propose a way to deal with Wittgenstein's problem of defining terms like "game"- or "chair". The basic idea was to probe further into what Wittgenstein was trying to do when he talked about "family resemblances" and tried to describe a game in terms of properties, the way one might treat members of a human family: build, features, colour of eyes, gait, temperament, etc. In my view, Wittgenstein missed the point because he focussed on "structure" only. What we have to do is also take into account the "function", "goal", or "intended use" of the definition. My trick is to catch the idea between two descriptions, structural and functional. Consider a chair, for example. STRUCTURE: A chair usually has a seat, back, and legs - but any of them can be changed in so many ways that it is hard to make a definition to catch them all. FUNCTION: A chair is intended to be used to keep one's bottom about 14 inches off the floor, to support one's back comfortably, and to provide space to bend the knees. If you understand BOTH of these, then you can make sense of that list of structural features - seat, back, and legs - and engage your other worldly knowledge to decide when a given object might serve well as a chair. This also helps us understand how to deal with "toy chair" and such matters. Is a toy chair a chair? The answer depends on what you want to use it for. It is a chair, for example, for a suitable toy person, or for reminding people of "real" chairs, or etc. In other words, we should not worship Wittgenstein's final defeat, in which he speaks about vague resemblances - and, in effect, gives up hope of dealing with such subjects logically. I suspect he simply wasn't ready to deal with intentions - because nothing comparable to Newell and Simon's GPS theory of goals, or McCarthy's meta-predicate (Want P) was yet available. I would appreciate comments, because I think this may be an important theory, and no one seems to have noticed it. I just noticed, myself, that I didn't mention Wittgenstein himself (on page 130) when discussiong the definition of "game". Apologies to his ghost.