_Its origin: the theory of play, and its variants—Æsthetic activity is the play of the creative imagination in its disinterested form. Its instinctive nature—Transition from simple play to æsthetic play: primitive art of pantomimic dancing—Derivation of the arts in motion; of the arts at rest—Why was æsthetic activity evolved?—Art had, in the beginning, a social utility—Evolution of the æsthetic sentiment—Its sociological aspect: progression from the strictly social character towards individualism in the different arts—Its anthropological aspect: progress from strictly human character towards beings and things as a whole—The feeling for nature—The feeling for the sublime only partially belongs to æsthetics—Its evolution: it is not æsthetic in its origin, but becomes so—Why there are not two æsthetic senses—The sense of the comic—Psychology of laughter—It has more than one cause—Theory of superiority. Theory of discord—These correspond to two distinct stages, one of which is foreign to æsthetics—Physiology of laughter. Theory of nervous derivation—Theory of tickling—Pathology. Are there cases of complete æsthetic insensibility? Difficulties and transpositions of the subject—Pathological function of emotion: pessimistic tendencies, megalomania, influence of unconscious activity—Pathological aspects of the creative imagination; its degrees—Reason why the intense image, in artists, does not pass into action; ways in which it is modified—Cause of this deviation; its advantages._ While all the emotions hitherto enumerated have their origin and their _raison d’être_ in the preservation of the individual as an individual, or as a social being, the æsthetic feeling, as we know, differs from the rest by the fact that the activity which produces it, aims, not at the accomplishment of a vital or social function, but at the mere pleasure of exercising itself. The more directly a tendency is connected with life, the more necessary, urgent, and serious it is, and the less it paves the way for the æsthetic feeling, which must always have a surplus to expend. However, its inutility, which is only relative, has been exaggerated; for it tends in some measure to the conservation of the individual and the race, being, and especially having been in the past, a _social_ factor, though an incidental and subordinate one, as we shall see afterwards. In conformity with the plan adopted, we shall remain strictly within the bounds of psychology, avoiding any excursions into the history or theory of art, except for the purpose of seeking facts and illustrations. We shall thus have to study the origin of æsthetic emotion, the law of its development, and, subsequently, two forms of emotional life, rightly or wrongly, considered as related to it: the sense of the sublime and that of the comic; and we shall conclude by some remarks on its morbid manifestations.