These two reasons sufficiently explain the tendency to see only psychological states in the emotional ones; and, in fact, those authors who have sought to oppose mind to matter have not failed to introduce emotion into their parallel as representing the essence of mind. On this point I will recall the fine ironical image used by Tyndall, the illustrious English physicist, to show the abyss which separates thought from the molecular states of the brain. "Let us suppose," he says, "that the sentiment love, for example, corresponds to a right-hand spiral movement of the molecules of the brain and the sentiment hatred to a left-hand spiral movement. We should then know that when we love, a movement is produced in one direction, and when we hate, in another. But the Why would remain without an answer."
The question of knowing what place in our metaphysical theory we ought to secure for emotion seems difficult to resolve, and we even find some pleasure in leaving it in suspense, in order that it may be understood that a metaphysician is not compelled to explain everything. Besides, the difficulties which atop us here are peculiarly of a psychological order. They proceed from the fact that studies on the nature of the emotions are still very little advanced. The physical conditions of these states are pretty well known, and their psychical and social effects have been abundantly described; but very little is known as to what distinguishes an emotion from a thought.
Two principal opinions may be upheld in the actual state of our acquaintance with the psychology of the feelings. When we endeavour to penetrate their essential and final nature, we have a choice between two contrary theories.
The first and traditional one consists in seeing in emotion a phenomenon _sui generis_; this is very simple, and leaves nothing more to be said.
The second bears the name of the intellectualist theory. It consists in expunging the characteristic of the affective states. We consider them as derivative forms of particular modes of cognition, and they are only "confused intelligence." This intellectualist thesis is of early date; it will be found in Herbart, who, by-the-by, gave it a peculiar form, by causing the play of images to intervene in the formation of the feelings. However, this particular point is of slight Importance. The intellectualist theory is more vast than Herbartism; it exists in all doctrines in which the characteristic difference between thought and feeling is expunged and feeling is brought back to thought. One of the clearest means of so doing consists in only seeing in the feeling the fact of perceiving something. To perceive is, in fact, the property of intelligence; to reason, to imagine, to judge, to understand, is always, in a certain sense, to perceive. It has been imagined that emotion is nothing else than a perception of a certain kind, an intellectual act strictly comparable to the contemplation of a landscape. Only, in the place of a landscape with placid features you must put a storm, a cataclysm of nature; and, instead of supposing this storm outside us, let it burst within us, let it reach us, not by the outer senses of sight and condition, but by the inner senses. What we then perceive will be an emotion.