The attitude of physiological psychology to sensations and feelings, considered as psychical elements, is, naturally, the attitude of psychology at large.

Many psychologists ... thought by turning their attention to their own consciousness to be able to explain what happened when we were thnking. Or they sought to attain the same end by asking another person a question, by means of which certain processes of thought would be excited, and then by questioning the person about the introspection he had made. It is obvious ... that nothing can be discovered in such experiments.

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.

The attitude of physiological psychology to sensations and feelings, considered as psychical elements, is, naturally, the attitude of psychology at large.

The task of physiological psychology remains the same in the analysis of ideas that it was in the investigation of sensations: to act as mediator between the neighbouring sciences of physiology and psychology.

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.