Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!rutgers!ucla-cs!zen!ucbvax!BBN.COM!aweinste From: aweinste@BBN.COM (Anders Weinstein) Newsgroups: comp.ai.digest Subject: Re: Natural Kinds (Re: AIList Digest V5 #186) Message-ID: <7548@diamond.BBN.COM> Date: Thu, 30-Jul-87 12:25:29 EDT Article-I.D.: diamond.7548 Posted: Thu Jul 30 12:25:29 1987 Date-Received: Mon, 3-Aug-87 03:53:18 EDT References: Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: aweinste@bbn.com (Anders Weinstein) Distribution: world Organization: BBN Laboratories Incorporated, Cambridge, MA Lines: 45 Approved: ailist@stripe.sri.com In article MINSKY@OZ.AI.MIT.EDU writes: > >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. I think there's some confusion about what natural kinds are in this discussion. Most of the talk has focussed on the alleged sharpness of the kind's boundaries. But I don't think this is what's at issue, at least in the contemporary philosophical usage. The point is that you can't do science without imposing some taxonomy on the objects under study. "Natural kinds" are simply the kinds that figure in scientific generalizations (aka Laws of Nature). Thus "bird" is perhaps a natural kind, but "thing that is either furry or made of clay" is not. Some people like to argue about whether these classification systems are "out there" in Nature waiting to be discovered (the "realist" view) or are invented by the mind and imposed on some undifferentiated reality (an "idealist" or "constructivist" picture). Happily, we can ignore this debate. What we can't ignore is the fact that a notion of natural kinds is *essential* for induction, as demonstrated by Nelson Goodman's classic "grue vs green" puzzle. Without some sense of what kinds are "natural", you're liable to go off projecting "grue", or looking for laws governing "furry or clay things". This would be the antithesis of intelligence. Of course, coming up with suitable taxonomies is an empirical matter. I once heard Kuhn emphasize that Aristotle's concept of "motion" included things like the growth of trees. Progress in physics had to await a more useful concept of motion. But this shouldn't be taken to imply that natural kinds are only relevant to sophisticated scientific theorizing -- the same principles apply to the inductions that are part of common-sense understanding. And it seems that we are blessed with pretty accurate innate intuitions about which kinds or similarities are natural (eg. "green") and which are ludicrously artificial ("grue"). The philosophy of induction thus suggests that you can't make an intelligent system without somehow building into it an equivalent sense of the naturalness of kinds. Anders Weinstein BBN Labs