Abstract
This chapter deals with the ontology of bodies in Locke’s Essay. In Descartes’s ontology, a created substance, or its principal attribute, unifies the many modes that belong to that substance; by contrast, Locke’s ontology includes not only substances and their qualities, but also composite entities which contain substances but are unified by modes. Locke, it is argued, seeks to adapt the apparent unity of living things, e.g. oaks, horses, and human beings, to the (Cartesian) mechanistic doctrine that matter is a substance. His concepts of inner constitution and identity are designed to give a metaphysical account of the unity of the ordinary entities that are salient in our experience. There is nothing corresponding to this in the Cartesian texts. They purport to explain the unity among qualities of mercury, salt, etc., and the processes carried on by plants and animals on the basis of physical theory, not metaphysics.