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

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

Heredity provides for the modification of its own machinery.

In the first place, Descartes stands for the most explicit and uncompromising dualism between mind and matter.

Psychology more than any other science has had its pseudo-scientific no less than its scientific period.

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.

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