To sum up, every event of this kind, reduced to its simplest expression, consists in (1) an intellectual fact, analogous to a spring moving the whole machine, (2) an unconscious, half-conscious, or conscious reaction of the instinct of self-preservation; this being by no means an entity, as we have already said, but the organism itself under its dynamic aspect. 2nd Period.—_Perceptions, images, or ideas connected with social conditions of existence._ Up to the present, we have only considered emotional reaction in its relations with nature—_i.e._, with the physical environment. Its domain is much more extensive; in man, and in many animals, it is adapted to the social environment. At bottom, the mechanism remains the same. A perception, an image, or an idea excites an emotion, because related, directly or indirectly (in the latter case the relation is conceived, inductively or deductively), to the social conditions of the individual. The natural _ego_ has its needs and tendencies; the same is true of the social _ego_, grafted on the other, or rather, one with it; consequently, the mechanism comes very frequently into play; the circumference is extended, but the centre remains the same. Let us note the differences between the two periods. In the latter we have (1) a preponderance of representations and concepts—_i.e._, the superior forms of knowledge; (2) instead of a natural, innate association between certain perceptions and certain emotional reactions—associations which may be called anatomical, because fixed in the individual organism—there are secondary, acquired associations, less solidly fixed, sometimes entirely artificial, which result from experience, from education, from habit, from imitation. I give some examples, by way of elucidation, and in order to avoid repetition. The feeling of property is derived from a natural condition of existence—nutrition. It is first manifested—in the form of a prevision—in some animals who store up a reserve of food for the future. In primitive man this instinct extends to clothes, weapons, the cave or hut which he inhabits; later on, with the nomadic life, to herds and flocks; then to agricultural products, silver, gold, paper money; finally to that impalpable thing called credit, which has merely an imaginary existence. Thus it gradually takes on a social character. The knowledge of any loss or any gain, actual or possible, produces an emotion in the individual, because it shows him that his adaptation to social conditions is diminished or augmented.