and ahistorical. But it is not clear that all essential properties need to Three Ways of Resisting Essentialism about Natural Kinds

Essentialism about natural kinds has three tenets. The first tenet is that all and only members of a natural kind have some essential properties. The second tenet is that these essential properties play a causal role. The third tenet is that they are explanatorily relevant. I examine the prospects of questioning these tenets and point out that arguing against the first and the second tenets of kind-essentialism would involve taking part in some of the grand debates of philosophy. But, at least if we restrict the scope of the discussion to the biological domain, the third tenet of kind-essentialism could be questioned more successfully. It is not an easy task to pin down what is meant by essentialism about natural kinds (Putnam 1975; Kripke 1980). First, one can be essentialist about individuals and about kinds. I will not say anything here about essentialism regarding individuals. Maybe, as Kripke claims, specific indi-viduals have essential properties, maybe not (on this important and complex question, see, for example, Robertson 1998; Hawthorne and Gendler 2000; Matthen 2003). Essentialism about individuals is logically independent from essentialism about kinds (see also Okasha 2002, 192). The question I am interested in is whether natural kinds have essential properties. Second, there are a number of potential definitions for essentialism about kinds. As I intend to argue against essentialism, I will use the most general of these. Richard Boyd identified a widespread and fairly strong version of essentialism, according to which natural kinds “must possess definitional essences that define them in terms of necessary and suffi-cient, intrinsic, unchanging, ahistorical properties ” (Boyd 1999, 146). Essential properties in, say, chemistry may all be intrinsic, unchanging