Story of Psychology - Morton Hunt [41]
Earlier dualistic philosophers had ignored this problem; the physiologically aware Descartes could not. From his and others’ anatomical studies, he knew that the brain has two identical hemispheres but that deep within it is a tiny gland (the pineal body); because this is single, like the soul itself, and because of its position in the brain, it seemed to him the obvious junction of soul and body. He conjectured that, due to its position in the brain, “its slightest motions can greatly affect the flow of the spirits, and conversely the slightest changes in the flow of the spirits greatly affect the motions of the gland.”11 While he never explained how the corporeal pineal gland and the incorporeal soul could make contact, he felt sure that they did and that it was through the gland that the soul affected the body, and the body the soul:
The whole action of the mind [i.e., soul] consists in this, that by the simple fact of its willing anything it causes the little gland, to which it is closely joined, to produce the result appropriate to the volition12 … [Conversely,] the movements [of the gland] which are excited in the brain by the nerves affect in diverse ways the soul or mind, which is intimately connected with the brain, according to the diversity of the motions themselves.13
The body thus engenders in the soul such passions as love, hatred, fear, and desire. The soul consciously considers each passion and freely wills to act in response to it—or, if it deems the passion undesirable, to ignore it. Why, then, do we ever do wrong? Not because the soul chooses to or is in conflict with itself, said Descartes, but because very intense passions may produce “commotions” of the animal spirits that override the soul’s control of the pineal gland, eliciting responses contrary to the soul’s judgment and will.
But one of Descartes’ major goals in setting forth his psychology was to show how to control the passions through reason and will. He offered much sensible advice, such as when powerful passion is aroused, one should deliberately divert one’s attention elsewhere until the agitation calms down, and only then make a judgment as to what to do. Most of what he said about controlling the passions is on this level; it is the least interesting part of his psychology.
He classified the passions, but without giving any illuminating theory as to their origins. There are six primary ones—wonder, love, hate, desire, joy, and sadness—all the rest being varieties or combinations of these. Unlike his dramatic description of his search for a first philosophic principle, his discussion of the passions was definitional and dry as dust. A single example will serve:
Love is an emotion of the soul, caused by the motion of the spirits, which incites it to unite itself voluntarily to those objects which appear to it to be agreeable. And hatred is an emotion, caused by the spirits, which incites the mind to will to be separated from objects which present themselves to it as harmful.14
Although Descartes’ explanation of the interaction between body and soul is quite wrong—the pineal gland, which produces melatonin and influences vision and sleep, has no influence on either efferent or afferent nervous impulses—the mechanical details are unimportant. What is important is his theory that body and mind are separate entities, composed of different substances, which interact in a living person, sometimes harmoniously, sometimes competitively, and that this competition is the most crucial aspect of human existence. The theory greatly influenced the human search for self-understanding, but not for the better. Raymond Fancher, a historian of psychology, sums up the weakness and the power of Descartes’ dualistic theory:
On the one hand, he taught that a person was a machine, capable of being studied by the methods of natural science. On the other hand, he taught that the most valuable and unique human attribute, the soul, was beyond the reach of scientific method and