When French philosopher Nicolas Malebranche (1638-1715) set forth his opposition to Descartes' view that mind is better known than body, he touched off a controversy that had prominent fellow Cartesians accusing him of both failed logic and dubious theology. Malebranche responded by asserting that his negative thesis concerning our knowledge of mind derived from his superior grasp of Cartesian theory and signalled neither a rejection of Descartes' philosophical system nor a denial of properties of the soul such as spirituality, immortality, and freedom. The current resurgence of interest in Malebranche's work has led to a greater understanding of his account of ideas, his notorious doctrine of "the Vision of all things in God," but has left unexplored crucial aspects of his theory of the soul and the precise nature of its Cartesianism. This vital new book confronts these matters directly, arguing provocatively that Malebranche was correct in claiming a Cartesian foundation for his theory and demonstrating the value to Cartesian studies of Malebranche's uniquely internal critique of Descartes' account of body and mind.