Society exists wherever several individuals are in reciprocal relationship. This reciprocity arises always from specific impulses or by virtue of specific purposes. Erotic, religious, or merely associative impulses, purposes of defense or of attack, of play as well as of gain, of aid and instruction, and countless others bring it to pass that men enter into group relationships of acting for, with, against, one another; that is, men exercise an influence upon these conditions of association and are influenced by them. These reactions signify that out of the individual bearers of those occasioning impulses and purposes a unity, that is, a "society," comes into being.

An organic body is a unity because its organs are in a relationship of more intimate interchange of their energies than with any external being. A state is one because between its citizens the corresponding relationship of reciprocal influences exists. We could, indeed, not call the world one if each of its parts did not somehow influence every other, if anywhere the reciprocity of the influences, however mediated, were cut off. That unity, or socialization, may, according to the kind and degree of reciprocity, have very different gradations, from the ephemeral combination for a promenade to the family; from all relationships "at will" to membership in a state; from the temporary aggregation of the guests in a hotel to the intimate bond of a medieval guild.

Everything now which is present in the individuals—the immediate concrete locations of all historical actuality—in the nature of impulse, interest, purpose, inclination, psychical adaptability, and movement of such sort that thereupon or therefrom occurs influence upon others, or the reception of influence from them—all this I designate as the content or the material of socialization. In and of themselves, these materials with which life is filled, these motivations which impel it, are not social in their nature. Neither hunger nor love, neither labor nor religiosity, neither the technique nor the functions and results of intelligence, as they are given immediately and in their strict sense, signify socialization. On the contrary, they constitute it only when they shape the isolated side-by-sideness of the individuals into definite forms of with-and-for-one-another, which belong under the general concept of reciprocity. Socialization is thus the form, actualizing itself in countless various types, in which the individuals—on the basis of those interests, sensuous or ideal, momentary or permanent, conscious or unconscious, casually driving or purposefully leading—grow together into a unity, and within which these interests come to realization.

That which constitutes "society" is evidently types of reciprocal influencing. Any collection of human beings whatsoever becomes "society," not by virtue of the fact that in each of the number there is a life-content which actuates the individual as such, but only when the vitality of these contents attains the form of reciprocal influencing. Only when an influence is exerted, whether immediately or through a third party, from one upon another has society come into existence in place of a mere spatial juxtaposition or temporal contemporaneousness or succession of individuals. If, therefore, there is to be a science, the object of which is to be "society" and nothing else, it can investigate only these reciprocal influences, these kinds and forms of socialization. For everything else found within "society" and realized by means of it is not "society" itself, but merely a content which builds or is built by this form of coexistence, and which indeed only together with "society" brings into existence the real structure, "society," in the wider and usual sense.

The persistence of the group presents itself in the fact that, in spite of the departure and the change of members, the group remains identical. We say that it is the same state, the same association, the same army, which now exists that existed so and so many decades or centuries ago; this, although no single member of the original organization remains. Here is one of the cases in which the temporal order of events presents a marked analogy with the spatial order. Out of individuals existing side by side, that is, apart from each other, a social unity is formed. The inevitable separation which space places between men is nevertheless overcome by the spiritual bond between them, so that there arises an appearance of unified interexistence. In like manner the temporal separation of individuals and of generations presents their union in our conceptions as a coherent, uninterrupted whole. In the case of persons spatially separated, this unity is effected by the reciprocity maintained between them across the dividing distance. The unity of complex being means nothing else than the cohesion of elements which is produced by the reciprocal exercise of forces. In the case of temporally separated persons, however, unity cannot be effected in this manner, because reciprocity is lacking. The earlier may influence the later, but the later cannot influence the earlier. Hence the persistence of the social unity in spite of shifting membership presents a peculiar problem which is not solved by explaining how the group came to exist at a given moment.

a) Continuity by continuance of locality.—The first and most obvious element of the continuity of group unity is the continuance of the locality, of the place and soil on which the group lives. The state, still more the city, and also countless other associations, owe their unity first of all to the territory which constitutes the abiding substratum for all change of their contents. To be sure, the continuance of the locality does not of itself alone mean the continuance of the social unity, since, for instance, if the whole population of a state is driven out or enslaved by a conquering group, we speak of a changed civic group in spite of the continuance of the territory. Moreover, the unity of whose character we are speaking is psychical, and it is this psychical factor itself which makes the territorial substratum a unity. After this has once taken place, however, the locality constitutes an essential point of attachment for the further persistence of the group. But it is only one such element, for there are groups that get along without a local substratum. On the one hand, there are the very small groups, like the family, which continue precisely the same after the residence is changed. On the other hand, there are the very large groups, like that ideal community of the "republic of letters," or the other international associations in the interest of culture, or the groups conducting international commerce. Their peculiar character comes from entire independence of all attachment to a definite locality.

b) Continuity through blood relationship.—In contrast with this more formal condition for the maintenance of the group is the physiological connection of the generations. Community of stock is not always enough to insure unity of coherence for a long time. In many cases the local unity must be added. The social unity of the Jews has been weakened to a marked degree since the dispersion, in spite of their physiological and confessional unity. It has become more compact in cases where a group of Jews have lived for a time in the same territory, and the efforts of the modern "Zionism" to restore Jewish unity on a larger scale calculate upon concentration in one locality. On the other hand, when other bonds of union fail, the physiological is the last recourse to which the self-maintenance of the group resorts. The more the German guilds declined, the weaker their inherent power of cohesion became, the more energetically did each guild attempt to make itself exclusive, that is, it insisted that no persons should be admitted as guildmasters except sons or sons-in-law of masters or the husbands of masters' widows.

The physiological coherence of successive generations is of incomparable significance for the maintenance of the unitary self of the group, for the special reason that the displacement of one generation by the following does not take place all at once. By virtue of this fact it comes about that a continuity is maintained which conducts the vast majority of the individuals who live in a given moment into the life of the next moment. The change, the disappearance and entrance of persons, affects in two contiguous moments a number relatively small compared with the number of those who remain constant. Another element of influence in this connection is the fact that human beings are not bound to a definite mating season, but that children are begotten at any time. It can never properly be asserted of a group, therefore, that at any given moment a new generation begins. The departure of the older and the entrance of the younger elements proceed so gradually and continuously that the group seems as much like a unified self as an organic body in spite of the change of its atoms.

If the change were instantaneous, it is doubtful if we should be justified in calling the group "the same" after the critical moment as before. The circumstance alone that the transition affected in a given moment only a minimum of the total life of the group makes it possible for the group to retain its selfhood through the change. We may express this schematically as follows: If the totality of individuals or other conditions of the life of the group be represented by a, b, c, d, e; in a later moment by m, n, o, p, q; we may nevertheless speak of the persistence of identical selfhood if the development takes the following course: a, b, c, d, e—m, b, c, d, e—m, n, c, d, e—m, n, o, d, e—m, n, o, p, e—m, n, o, p, q. In this case each stage is differentiated from the contiguous stage by only one member, and at each moment it shares the same chief elements with its neighboring moments.