Abstract

Locke has been accused of endorsing a theory of kinds that is inconsistent with his theory of individuation. This purported inconsistency comes to the fore in Locke’s treatment of cases involving organisms and the masses of matter that constitute them, for example, the case of a mass constituting an oak tree. In this essay, I argue that this purported problem, known as ‘The Kinds Problem’, can be solved. The Kinds Problem depends on the faulty assumption that nominal essences include only features observable at a time t. Once this assumption is rejected, new candidates open up for the relevant difference in the world that is included in the nominal essence of e.g. mass but not oak tree. And I argue that there is at least one good candidate for the extrinsic feature observable only over time in which the mass differs from the oak it constitutes, namely its persistence conditions. The Kinds Problem can be solved.