 It is universally agreed that Locke thinks that we sort things into species and genera based on nominal essences and species and genera are a kind of human linguistic categorization process. On the other hand, one might think, Locke has no reason to reject natural kinds (which concern the metaphysics of nature, and not the meanings of names) simply because our sorting process is arbitrary. In other words, there are those who argue that Locke was a natural kind realist, even though he was convinced that taxonomies are the workmanship of the understanding. Whether Locke thinks that there are natural kinds, i.e., types of real essences independently of human sorting activities, is an interpretive issue we shall address in  4.3 below.