The Passions may be seen as a continuation of the Treatise of man, except that the direction of approach is different. The Treatise of man starts with the body and announces that the soul will be treated later. The conclusion would probably have been that we are indistinguishable from the hypothetical “men who resemble us” with which the Treatise of man is concerned and that we are just such machines equipped with a rational soul ourselves. In the Passions, Descartes starts from the other end, with man, and begins by splitting man up into a body and a soul.