Our interest in natural kinds is generated by the fact that the particular sciences make frequent use of what, on the face of it, seem to be natural kinds. So an important question is whether the kinds of the special sciences (e.g. psychology, economics, biology, chemistry and so on) do in fact satisfy the conditions laid out by metaphysicians for natural-kindhood (Fodor 1974; Dupré 1981, 1993; Millikan 1999; Ellis 2001). And to the extent that they do not, does that show that these kinds are no