Locke on Individuation and the Corpuscular Basis of Kinds1

In this paper, I examine the crucial relationship between Locke’s theory of individuation and his theory of kinds. Locke holds that two material objects—e.g., a mass of matter and an oak tree—can be in the same place at the same time, provided that they are ‘of different kinds’. According to Locke, kinds are nominal essences, that is, general abstract ideas based on objective similarities between particular individuals. I argue that Locke’s view on coinciding material objects is incompatible with his view on kinds. In order for two material objects to be in the same place at the same time, they must differ with respect to at least one nominal essence. However, Locke thinks that it is impossible that x and y have the same real essence but differ with respect to any nominal essence; and coinciding material objects have the same real essence. Therefore, Locke cannot hold what he in fact holds, namely that distinct material objects can be in the same place at the same time.