The animal kingdom exhibits a series of mental developments which may be regarded as antecedents to the mental development of man, for the mental life of animals shows itself to be throughout, in its elements and in the general laws governing the combination of the elements, the same as the mental life of man.

The materialistic point of view in psychology can claim, at best, only the value of an heuristic hypothesis.

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

Psychology, on the other hand, seeks to give account of the interconnexion of processes which are evinced by our own consciousness, or which we infer from such manifestations of the bodily life in other creatures as indicate the presence of a consciousness similar to our own.

In the animal world, on the other hand, the process of evolution is characterised by the progressive discrimination of the animal and vegetative functions, and a consequent differentiation of these two great provinces into their separate departments.

The general statement that the mental faculties are class concepts, belonging to descriptive psychology, relieves us of the necessity of discussing them and their significance at the present stage of our inquiry.

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.