INTRODUCTION. THE EVOLUTION OF THE AFFECTIVE LIFE. _In all affective manifestations there are two elements: the motor states or impulses, which are primary; the agreeable or painful states, which are secondary—Unconscious organic protoplasmic sensibility; microorganisms—Chemical interpretation; psychological interpretation—Are there pure states of feeling?—Affirmative facts—The period of needs, the instinct of conservation—The period of primitive emotions—How they may be determined; the genetic or chronological method—Fear, anger, affection, the self-feeling, sexual emotion—Are joy and grief emotions?—The abstract emotions and their conditions—The passions are the equivalent in feeling of an intellectual obsession._ At the outset it may be useful to sketch in rough outline the general evolution of the life of feeling from its humble origin in organic sensibility to its highest and most complex forms. Afterwards we shall present the corresponding and inverse picture, that of its dissolution. If we take at random, in the form in which daily experience gives them to us, the states known under the vague names of “sentiments,” “emotions,” “passions”: joy and sorrow, a toothache, a pleasurable perfume, love or anger, fear or ambition, æsthetic enjoyment or religious emotion, the rage of gambling or benevolence, the shudder of the sublime or the discomfort of disgust, and so on, for they are innumerable, one first observation is obvious even on a superficial examination: all these states, whatever they may be, offer a double aspect, objective or external, subjective or internal. We note in the first place the _motor_ manifestations: movements, gestures, and attitude of the body, a modification in the voice, blushing or pallor, tremors, changes in the secretions or excretions, and other bodily phenomena, varying in different cases. We may observe them in ourselves, in our fellows, and in animals. Although they may not always be motor in the strict sense, we may so call them, since they are all the result of a centrifugal action. We note also, in ourselves directly and by the evidence of consciousness, in others indirectly and by induction, the existence of certain states which are agreeable, painful, or mixed, with their modes or shades, extremely variable in quality and in intensity. Of these two groups—the motor manifestations on one side, the pleasures, pains, and their compounds on the other side—which is fundamental? Can we put them on the same level, and if we cannot, which is that which supports the other?