Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!columbia!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: Mon, 27-Jul-87 11:16:00 EDT Article-I.D.: MIT-OZ.MINSKY.12321721233.BABYL Posted: Mon Jul 27 11:16:00 1987 Date-Received: Fri, 31-Jul-87 00:43:46 EDT References: Sender: daemon@ucbvax.BERKELEY.EDU Distribution: world Organization: The ARPA Internet Lines: 48 Approved: ailist@stripe.sri.com I agree: 1. Yes, I think we'd all agree that a chair is for 1 person to sit on. 2. The boundary is fuzzy, indeed, and some people might not consider a Balenz chair to be a chair. 3. Yes, indeed, the "functional description" does indeed depend on whose "intention" is ivolved, and upon who is saying what to whom. My point is not that such terms can be defined in foolproof, clear-cut ways. There are really two sorts of points. 1. You can get much further in making good definitions by squeezing in from both structural and function directions - and surely others as well. 2. In Society of Mind, section 30.1 I discuss how meanings must depend on speakers, etc. As Ken Laws remarked, we should not be too hasty to thank philosophers for concept of "natural kind". McCarthy make useful remarks about penguins, which form a clear-cut cluster because of the speciation mechanism of sexual reproduction. The class is un-fuzzy even though, as McCarthy notes, penguins have properties that scientists have not yet discovered. But then, I think, McCarthy defeats this clarity by proceeding to discuss how children learn about chairs - and tries to subsume this, too, into natural kinds. He describes what seems clearly to be not "natural" aspects of chairs, but the clustering and debugging processes a child might use. My conclusion - and, I'd bet, Ken Laws would agree - is that the concept of "natural kind" has an illusory generality. It seems to me that, rather than good philosophy, it is merely low-grade science contaminated by naive, traditional common sense concepts. The clusters that have good boundaries, in the world, usually have them for good - but highly varied reasons. Animals form good clusters because of Darwinian speciation of various sorts. Certain metals, like Gold, have "natural" boundaries because of the Pauli exclusion principle which causes things like periodic tables of elements. Philosophers like to speak about gold - but their arguments won't work so well for Steel, whose boundary is fuzzy because there are so many ways to strengthen iron. All in all, the clusters we perceive that have sharp boundaries are quite important, pragmatically, but exist for such a disorderly congeries of reasons that I consider the philosophical discussion of them to be virtually useless in this sense: the class of clusters with "suitable sharp boundaries" to desaerve the title "natural kinds" is itself too fuzzy a concept to help us clarify the nature of how we think about things.