PROLEGOMENA TO SOCIAL PSYCHOLOGY 99
of the one is necessary to the understanding of the other ; and it is only the possibility of two points of view, of two centers of interest, which makes possible any division of labor between the psychology which considers the individual and the psychol- ogy which studies the group-life. So long as the center of interest is in the individual — in explaining his psychical consti- tution, activities, and development — we are in the field of indi- vidual psychology, no matter what the subject-matter that we are dealing with objectively may be. But whenever the center of interest is in the group, in explaining its organization, activi- ties, and development, we are in the field of social psychology. Thus, individual psychology has a perfect right to consider the psychical life of the group in order to throw light upon the indi- vidual mind ; while social psychology must study the individual, because the whole with which it deals is a complex made up of individual elements. An illustration from the history of bio- logical science may serve to make our meaning clearer. At one time it was thought that in order to understand the organism it was necessary only to study the cell ; that from the nature of the cell the development, structure, and activities of the whole organism could be explained. It is now generally admitted, however, that the organism cannot be explained from the point of view of the cell alone, but that the point of view of the organism as a whole must also be taken if we are to understand many things concerning its structure and development. The organism is no longer regarded merely as the sum of cellular activities, but rather as a single process. Thus, modern biology studies the organism as a functional unity as well as an aggrega- tion of cells, using the one point of view to supplement the other. The analogous development in the history of the social sciences need hardly be pointed out. Individualism has assumed to be able fully to explain society from the nature of the indi- vidual ; but gradually it has been perceived that society itself must be regarded as an organic, functioning unity before the social process can be understood. As to its origin, then, social psychology is simply an expression of the need of considering the social process on its subjective side from the standpoint of
