one part must have its effect upon the whole society. Without theorizing about the existence of a mind over and above the minds of human individuals, it is recognized on all hands that there exists very concretely a social consciousness which forms the psychic environment of every individual. To this Zeitgeist, as well as to individual genius, must be attributed the achievements of a people, whether in the practical affairs of government, politics, and commerce, or in such intellectual products as literature and art. For, from this point of view, the individual is seen to exist no longer as an isolated unit but to stand in the closest reciprocal relations with the society about him. The whole content of his life,—religion, language, profession, customs,—is made up of the heritage which the past life of his society has accumulated for him and from which he can no more escape than from the physical peculiarities transmitted to him by his ancestors. Every thought and act has its origin in his social relations; and in turn, in its effects on his fellows, it is a contribution to the life and consciousness of the society of which he is a part. Apart from his social connections the individual is nothing; his individuality consists not in isolation but in the uniqueness of his social heritage and of his relations to other individuals.
The close relationship between these two concepts is obvious. The fact of continuity of development could scarcely be perceived so long as society was regarded as an agglomeration of individuals living in the same time and place, but still essentially separate and distinct in interest, and only superficially affected by the community in which they lived. Unity of development necessarily implies the unity of that which develops. On the other hand, it is scarcely conceivable that the notion of a social organism should have failed to bring with it also the idea of the growth of that organism and of the unity subsisting between the successive stages of its growth. The obvious fact that innovations are gradual and that they are not haphazard, but are directed by the organic character of the society in which they take place, would inevitably suggest that they might be expected to occur in a rational sequence, and that a discoverable unity would be found to exist between the states of society at different periods of time. Ac-
