Naturalism about natural kinds is the view that they are none other than the
kinds discoverable by science. This thesis is in tension with what is perhaps
the dominant contemporary view of natural kinds: essentialism. According
to essentialism, natural kinds constitute a small subset of our scientific categories, namely those definable in terms of intrinsic, microphysical
properties, which are possessed necessarily rather than contingently by their
bearers. Though essentialism may appear compatible with naturalism, and
is indeed sometimes qualified with the epithet “scientific,” it has become increasingly clear in recent years that only a minority of categories posited by
science satisfy those conditions. I will not try to argue against essentialism directly in this chapter. Instead, I will attempt to articulate an alternative, naturalist conception of natural kinds, according to which the mark of natural kinds is their discoverability by science, not just basic science but the special sciences and even the social sciences.