 La Forge began the Traité (1666) with a lengthy preface in which he compared Descartes’ theory of the human mind with that of Augustine, from whom he quoted extensively to show that the mind is a distinct substance that is immaterial and survives the death of the body. This immaterial substance has two characteristic properties, by which alone it is known: understanding and willing. The understanding can generate ideas or conceptions of realities that have never been observed or imagined, and to that extent it is independent of the human body. Pure understanding ‘is a faculty which is independent of the body in the same way as the will is’ (T 292; THM 188).