The problem of the person may be described as the crux of Descartes' philosophy in the fairly obvious literal sense that it is the point of intersection of the two chief axes of the system, the Philosophy of Nature and the Philosophy of Mind. The actual, if not professed aim of the former is the ousting of the occult powers and faculties of Scholastic-Aristotelian physics by the mechanical concept of force or action-by-contact. The chief tenet of the latter is that mind, whose essence is thinking, is clearly and distinctly conceivable apart from matter, the essence of which is extension. From this, by an illicit inference which need not concern us further, Descartes concludes that the mind is “really distinct” from matter, that is, a substance capable of existing apart from body in its own right. Where these two lines of thought meet, the problem of the person constitutes itself in the following manner.