Descartes, we saw, thought that he had managed to explain not only movement, breathing, digestion and other processes mechanically, by corpuscularian-hydraulic means, but also mental features such as memory and imagination, and even character traits and moods. And all these, according to him, do not involve any immaterial soul. Why, then, does he ascribe such a soul or mind to man? Why isn't Descartes' man just a biological machine?