1 64 THE AMERICAN JOURNAL OF SOCIOLOGY
contagion, influence, as forms of the interaction of mind with mind, may themselves be accounted for. It explains them as modes of example and imitation. All society is thus resolved into products of imitation.
In strict psychological analysis these "impression" and "imitation" theories must be classed, I think, as scientifically developed forms of the "sympathy" theories of society, that may be traced back through the literature of political philosophy to very early days. They offer proximate explanations of the great social facts of resemblance, of mutuality, of solidarity; but do they, beyond a doubt, trace concerted activity back to its absolute origin? Above all, do they account not only for similarity, but also for variation, for the differentiation of communities into leaders and followers, for competition as well as for combination, for liberty as well as for solidarity?
The fourth conception, put forth some years ago by the present writer, should be classed as a developed form of the instinct theory, dating back to Aristotle's aphorism that man is a political animal. It assumes that the most elementary form of social relationship is discovered in the very beginning of mental phenomena. In its simplest form mental activity is a response of sensitive matter to a stimulus. Any given stimulus may happen to be felt by more than one organism, at the same or at different times. Two or more organisms may respond to the same given stimulus simultaneously or at different times. They may respond to the same given stimulus in like or in unlike ways; in the same or in different degrees; with like or with unlike promptitude; with equal or with unequal persistence. I have attempted to show that in like response to the same given stimulus we have the beginning, the absolute origin, of all concerted activity — the inception of every conceivable form of co-operation; while in unlike response, and in unequal response, we have the beginning of all those processes of individuation, of differentiation, of competition, which, in their endlessly varied relations to combination, to co-operation, bring about the infinite complexity of organized social life.
It is unnecessary to argue that this conception of society not
