The prehistorical and primitive period represents the true infancy of the mind.

In Socrates' thought the two marks of individual self-consciousness appear; it is practical and it is social.

The reason of the close concurrence between the individuals progress and that of the race appears, therefore, when we remember the dependence of each upon the other.

Heredity provides for the modification of its own machinery.

All along we find that social life - religion, politics, art - reflects the stages reached in the development of the knowledge of self; it shows the social uses made of this knowledge.

Like all science, psychology is knowledge; and like science again, it is knowledge of a definite thing, the mind.

Pythagoras took the next important step by subordinating the mere matter of nature to its essential principle of form and order, identifying the latter with reason or the soul.