Descartes on His Essence

H E HELD that he was a mind, a substance the whole essence of which was to think. This paper is about why Descartes held this thesis; it is also, perforce, about what the thesis means, and about the two related theses, that a body is a substance the whole essence of which is to be extended in length, breadth, and depth, and that minds and bodies, the only kinds of created substances, are entirely and absolutely distinct. In the first section of this paper I consider the meaning of Descartes's thesis against the background of his essentialism in general. The second and third sections are attempts to discern, respectively, the arguments of the second and sixth Meditations (and their counterparts), while the last section deals with certain remaining questions.