It may seem less than reasonable to reexamine an issue on which there is widespread agreement. What is more evident than the boundary that separates the social from the non-social? Common sense permits no doubt that social reality is composed of human affairs. This certitude of common sense informs our ordinary actions as well as our most elevated sentiments. Nor is the exclusively human nature of social reality seriously questioned in the main traditions of Western philosophy. The coincidence of the social order with the pattern of relations between human beings is taken for granted. One can hardly blame the social scientist for failing to investigate the origin and the significance of this division of reality with as much detached interest as he would devote to the study of more obviously "culture-bound" assumptions of common sense.