 According to David Armstrong (1997, 67–8) “The kinds mark true joints in nature. But it is not clear that we require an independent and irreducible category of universal to accommodate the kinds”. Armstrong’s view is naturalistic, since there are genuine natural divisions; but he is also resistant to realism. If there were natural kinds they would be universals. But the properties shared by all and only the members of a kind will typically be very complex. For example, he considers whether there is some description of human DNA. There may be, but it would be too complex to qualify as a genuine universal. And there is no reason to suppose that this complex universal would do any causal or nomic work. So there is not simply an identity between natural kinds and a subcategory of universals, the natural kind universals (e.g., the universal of being gold, or of being a human)—according to Armstrong’s argument there are no natural kind universals. He does concede that the case is stronger for basic kind universals, such as electronhood, where a few properties (the electron’s mass, charge, and spin) are individually necessary and jointly sufficient for kind membership.