The Mind–Body Interaction
Descartes believed that all animal behavior and internal processes could be explained mechanically, as could much human behavior and many human internal processes. There was, how- ever, an important difference between humans and other animals. Only humans possessed a mind that provided consciousness, free choice, and rationality. Furthermore, the mind was nonphysical and the body physical; that is, the body occupied space but the mind did not. In the process of arriving at the first principle of his philosophy—“I think, therefore I am”—Descartes believed that he had discovered the fact that the mind was nonmaterial. Descartes (1637/1956) described what he next deduced from this first principle:
I then examined closely what I was, and saw that I could imagine that I had no body, and that there was no world nor any place that I occupied, but that I could not imagine for a moment that I did not exist. On the contrary, from the very fact that I doubted the truth of other things, it followed very evidently and very certainly that I existed. On the other hand, if I had … ceased to think while all the rest of what I had ever imagined remained true, I would have had no reason to believe that I existed; therefore I concluded that I was a substance whose whole essence or nature was only to think, and which, to exist, has no need of space nor of any material thing. Thus it follows that this stimulated appropriate brain areas, causing animal spirits to flow to various muscles and thus bringing about the willed behavior.
Because the mind is free, it can inhibit or modify the reflexive behavior that the environ- ment would elicit mechanically. Emotions are related to the amount of animal spirits involved in a response; the more the animal spir its, the stronger the emotion. Emotions are experienced consciously as passions such as love, wonder, hate, desire, joy, anger, or sadness. According to Des- cartes, the will can and should control the passions so that proper conduct results. If, for example, anger is experienced and angry behavior is appro- priate, the mind will allow or even facilitate such behavior. If, however, such behavior is seen as inappropriate, the mind will attempt to inhibit it. In the case of an intense passion, the will may be unable to prevent the reflexive behavior, and the person will act irrationally.
