Descartes' Notion of the Union of Mind and Body

Descartes' Notion of the Union of Mind and Body DAISIE RADNER MANY PHILOSOPHERSHAVEHELD the view that man is a being composed of mind and body. This view involves two claims. One is that the mind is something distinct from the body. The other is that the mind and the body form a unity which is the man. Some philosophers have emphasized the former claim, while others have emphasized the latter. Aristotle and Aquinas insisted upon the unity of man, because otherwise phenomena such as sensation and voluntary movement, which involve the operation of both soul and body, could not be explained. They reconciled the dualism of soul and body to the unity of man by saying that the body and the soul are united as matter to form. The soul, as the substantial form of the body, is what makes the body an actually living organism. Plato and Augustine , on the other hand, emphasized the distinction between the soul and the body. That the soul is something distinct from the body, they believed to be apparent from the fact that what the soul knows best, it knows without the aid of any bodily operations. If the soul can know without the aid of the body, then the soul is neither a part nor an aspect of the body. On the contrary, it is an incorporeal thing, which is independent of and thus separable from the body. One who adopts the theory that the soul and the body are independent entities is faced with the task of explaining, in terms of that theory, the phenomena which make the unity of man plausible. Augustine explained the phenomena of sensation and voluntary movement in terms of the sours action upon the body. According to his conception of the causal situation, the inferior cannot act upon the superior. 1 Thus, if two unequal things are in a causal relation, the cause is the one which is superior and the effect the one which is inferior. The superiority of one thing to another is judged on the basis of its relative simplicity.2 Since the soul is simpler than the body, it is superior to the body. Thus in all cases in which the soul and the body are in a causal relation, it is the soul which acts upon the body. This includes the case of sensation; for sensation occurs only when the soul "directs the sense to the sensible thing and keeps the vision itself fixed upon it." a De immortalitate animae, 8 (14). 2 De quantitate animae, 14 (23). 3 De Trinitate, XI, 2 (5). [159] 160 HISTORY OF PHILOSOPHY Like Plato and Augustine, Descartes emphasizes the dualism of mind and body. This essay is an examination and assessment of Descartes' attempt to establish the unity of man in the face of his doctrine of the real distinction between mind and body. Descartes' proof of the real distinction between mind and body, and the criticisms to which it gives rise, will not be discussed here. Even if Descartes does not argue convincingly for his doctrine of the real distinction between mind and body, it is enough for our purposes to note that he believes this doctrine to be basic to his philosophical task. If matter is not something really distinct from mind, then the new science, which offers only mechanistic explanations, would not give an exhaustive account of the physical world. Similarly , if the mind were not something really distinct from matter, then the religious doctrine of personal immortality would be untenable. According to Descartes' doctrine of the real distinction between mind and body, it is not merely the case that the mind and the body can exist apart. They are two substances which have entirely different natures. The nature of the body is extension and the nature of the mind thought, and "there is nothing at all common to thought and extension." 4 The mind and the body are not capable of the same sorts of modifications. The mind is capable only of modifications of thought, and the body only of modifications of extension. Like Augustine, Descartes seeks to explain the phenomena which make the unity of man plausible, by appealing...