Linsky’s central point is correct; Kripke’s distinction between rigid and nonrigid designators can be extended in a straightforward way from singular terms to general terms. In both cases, for an expression to rigidly designate its extension is for it to designate the same extension with respect to every possible world-state (in which it has an extension at all). On this account, simple natural kind terms like water, gold, electricity, blue, and tiger – as well as ordinary general terms like bachelor, philosopher, automobile and triangle – designate the same extension with respect to each world-state. As I see it, however, the two differ importantly in the metaphysics of their designata. Whereas a term like bachelor designates a property that may be distinguished from other properties that are necessarily coextensive with it, natural kinds differ from one another only if there are possible world-states in which some of their instances are different. Intuitively this seems plausible; it is hard to imagine two distinct species of animal, two distinct substances, or two distinct colors which have precisely the same instances in every possible world-state. This is important for my linguistic model. Consider, for example, the color blue (which I take to be a natural kind). Color science tells us that the object-color blue is determined...