We have spoken of desire as an impulse, and we would include all emotion as impulse, for to impel is its function and action. Impulse is the will side of emotion as interest is its intellectual side. If I fear a man, this is my interest in him and impulse from him. True, we speak of being driven by “blind impulse”; but emotion cannot be blind, it can only be kindled by object imaged. Anything which actuates the will may very broadly but wrongly be called impulse, for impulse strictly connotes an emotion wave undirected and issuing at once in action. Where unforeseen ends are served, as when a hen driven by sensation of heat sits on eggs, we commonly but wrongly denominate it impulse. Without some representation there is no emotion and no impulse. So when standing over a precipice I say I have the impulse to throw myself down, this means that the depth wakens in me image of falling and an awful desire to realize the image, which impels the act. If I am merely giddy I will fall, but if I have the emotion-impulse I will throw myself down; I am not impelled by dizziness or any sensation, but the term denotes emotion as desire or fear. For the ordinary human mind desire seems in general a spontaneous and instinctive act. We do not make an effort in desiring, though desire like other mental functions undoubtedly arose in struggle. Originally this psychosis was a stress and strain activity; it was a rarely achieved emotion, just as the emotion of pleasurable appreciation of Beethoven’s music or Michael Angelo’s sculpture is for most minds a rare uplift of psychic force. Knowing as compound of presentation and representation and as involving emotion and volition, is, with us, within certain limits, an habitual spontaneous act of mind. I feel the pain from cold, without sensation of cold, as bare pain, as undifferentiated feeling of discomfort, I then feel cold, I feel cold object, I desire warmth, I will to draw near the stove; here is a progressive series of correlated psychoses which are constantly occurring in a spontaneous way in ordinary experience. But this psychic structure which operates so easily is really the outgrowth of ages of psychic evolution wherein the separate steps have been achieved and the correlation established only by the severest _nisus_.