Abstract

How we understand Descartes’s physics rests on how we interpret his ontological commitment to individual bodies, and in particular on how we account for their individuation. However, Descartes’s contemporaries as well as contemporary philosophers have seen Descartes’s account of the individuation of bodies as deeply flawed. In the first part of this paper, I discuss how the various problems and puzzles involved in Descartes’s account of the individuation of bodies arise, and the relevance of these problems for his physics. With an eye toward resolving these puzzles, I argue for an interpretation of the Cartesian ontology in which bodies are not individuated by motion but, instead, are mind-dependent. As part of this reading, I demonstrate the sense in which we can clearly and distinctly perceive bodies, and also the senses in which the real, conceptual, and modal distinctions apply to them. I conclude by explaining how this account of the mind-dependent individuation of bodies is consistent with Descartes’s definition of ‘motion’ and ‘a body’ in Principles, Part II, section 25—the very passage that prima facie entails the most troubling of the individuation puzzles. Finally, I show that this account is consistent with Descartes’s general goal in constructing his physics.