The old metaphysical prejudice that man 'always thinks' has not yet entirely disappeared. I am myself inclined to hold that man really thinks very little and very seldom.

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.

Physiology is concerned with all those phenomena of life that present them selves to us in sense perception as bodily processes, and accordingly form part of that total environment which we name the external world.

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, in its analysis of the physiological functions of the sense organs, must use the results of subjective observation of sensations; and psychology, in its turn, needs to know the physiological aspects of sensory function, in order rightly to appreciate the psychological.

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.