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

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

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

The dualism itself becomes a sort of presupposition or datum; its terms condition the further problem.

Heredity provides for the modification of its own machinery.

The fact that tradition hinders the individual savage from thinking logically by no means proves that he cannot think logically.

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.