From the point of view of observation, however, it is particularly difficult to distinguish the part played by tradition as a psychological influence from that played by what we have above described as instinctive imitation. In our study of other modes of instinctive behaviour we can isolate an individual, or group of young individuals, and observe how far certain acts are performed prior to any experience. Thus chicks behave in certain instinctive ways under conditions which preclude their learning from the hen or other older birds--so that tradition cannot be operative. But where social behaviour is concerned, such methods of observation are necessarily excluded, since isolation involves the absence of the social factor. And if certain instinctive acts require for their due performance the stimulus of the like performance in others, what is this but a form of instinctive tradition; and how are we to distinguish it from intelligent tradition, where a psychological factor has freer play and exercises guidance over the performance? In the present state of our knowledge we can do no more than suggest, as not improbable, that tradition passes through three phases: the first in which it is instinctive; the second in which it becomes intelligent through the satisfaction which the due performance of traditional acts arouses in consciousness; and the third in which, at any rate in man, it takes on a rational form, and is made to accord with an ideal scheme, the product of conceptual thought and of reflection on data which have been generalized and considered in their due relationships to the scheme which takes definite form in the mind. Whether in the social communities of insects or those of beavers, among mammals, or rooks among birds, tradition has begun to pass into the third or rational stage, we do not know. It may be so, but probably the development along these lines has not been carried far. Presumably in the ant, rook, and beaver anything like an ideal scheme of thought based on reflection, if it exist, is as yet exceedingly indefinite. But even supposing that no animal has yet risen beyond the second or intelligent stage, it is none the less important to realize that we have here, in animal life, the foundations on which may be raised what may, perhaps, be regarded as one of the characteristic features of human progress. This characteristic is the transference of evolution from the organism to the environment handed on from generation to generation. Thus man, “availing himself of tradition, is able to seize upon the acquirements of his ancestors at the point where they left them.”[106] Thus “he has slowly accumulated and organized the experience which is almost wholly lost with the cessation of individual life in other animals.”[107] But he is able to do so through the extension, refining, and fixing of that instinctive and intelligent tradition which begins to take form in animal communities. V.--THE EVOLUTION OF SOCIAL BEHAVIOUR