The life of man in society, just like the life of other species, is a struggle for existence, and therefore it is a process of selective adaptation. The evolution of social structure has been a process of natural selection of institutions. The progress which has been and is being made in human institutions and in human character may be set down, broadly, to a natural selection of the fittest habits of thought and to a process of enforced adaptation of individuals to an environment which has progressively changed with the growth of the community and with the changing institutions under which men have lived. Institutions are not only themselves the result of a selective and adaptive process which shapes the prevailing or dominant types of spiritual attitude and aptitudes; they are at the same time special methods of life and of human relations, and are therefore in their turn efficient factors of selection. So that the changing institutions in their turn make for a further selection of individuals endowed with the fittest temperament, and a further adaptation of individual temperament and habits to the changing environment through the formation of new institutions.
The forces which have shaped the development of human life and of social structure are no doubt ultimately reducible to terms of living tissue and material environment; but proximately for the purpose in hand, these forces may best be stated in terms of an environment, partly human, partly non-human, and a human subject with a more or less definite physical and intellectual constitution. Taken in the aggregate or average, this human subject is more or less variable; chiefly, no doubt, under a rule of selective conservation of favorable variations. The selection of favorable variations is perhaps in great measure a selective conservation of ethnic types. In the life history of any community whose population is made up of a mixture of divers ethnic elements, one or another of several persistent and relatively stable types of body and of temperament rises into dominance at any given point. The situation, including the institutions in force at any given time, will favor the survival and dominance of one type of character in preference to another; and the type of man so selected to continue and to further elaborate the institutions handed down from the past will in some considerable measure shape these institutions in his own likeness. But apart from selection as between relatively stable types of character and habits of mind, there is no doubt simultaneously going on a process of selective adaptation of habits of thought within the general range of aptitudes which is characteristic of the dominant ethnic type or types. There may be a variation in the fundamental character of any population by selection between relatively stable types; but there is also a variation due to adaptation in detail within the range of the type, and to selection between specific habitual views regarding any given social relation or group of relations.
For the present purpose, however, the question as to the nature of the adaptive process -- whether it is chiefly a selection between stable types of temperament and character, or chiefly an adaptation of men's habits of thought to changing circumstances -- is of less importance than the fact that, by one method or another, institutions change and develop. Institutions must change with changing circumstances, since they are of the nature of an habitual method of responding to the stimuli which these changing circumstances afford. The development of these institutions is the development of society. The institutions are, in substance, prevalent habits of thought with respect to particular relations and particular functions of the individual and of the community; and the scheme of life, which is made up of the aggregate of institutions in force at a given time or at a given point in the development of any society, may, on the psychological side, be broadly characterized as a prevalent spiritual attitude or a prevalent theory of life. As regards its generic features, this spiritual attitude or theory of life is in the last analysis reducible to terms of a prevalent type of character.
The situation of today shapes the institutions of tomorrow through a selective, coercive process, by acting upon men's habitual view of things, and so altering or fortifying a point of view or a mental attitude banded down from the past. The institutions -- that is to say the habits of thought -- under the guidance of which men live are in this way received from an earlier time; more or less remotely earlier, but in any event they have been elaborated in and received from the past.
Institutions are products of the past process, are adapted to past circumstances, and are therefore never in full accord with the requirements of the present. In the nature of the case, this process of selective adaptation can never catch up with the progressively changing situation in which the community finds itself at any given time; for the environment, the situation, the exigencies of life which enforce the adaptation and exercise the selection, change from day to day; and each successive situation of the community in its turn tends to obsolescence as soon as it has been established. When a step in the development has been taken, this step itself constitutes a change of situation which requires a new adaptation; it becomes the point of departure for a new step in the adjustment, and so on interminably.
