Physiology seeks to derive the processes in our own nervous system from general physical forces, without considering whether these processes are or are not accompanied by processes of consciousness.

Hence, wherever we meet with vital phenomena that present the two aspects, physical and psychical there naturally arises a question as to the relations in which these aspects stand to each other.

Psychology must not only strive to become a useful basis for the other mental sciences, but it must also turn again and again to the historical sciences, in order to obtain an understanding for the more highly developed metal processes.

Philosophical reflection could not leave the relation of mind and spirit in the obscurity which had satisfied the needs of the naive consciousness.

The distinguishing characteristics of mind are of a subjective sort; we know them only from the contents of our own consciousness.

Child psychology and animal psychology are of relatively slight importance, as compared with the sciences which deal with the corresponding physiological problems of ontogeny and phylogeny.

We speak of virtue, honour, reason; but our thought does not translate any one of these concepts into a substance.