Contractile movements arise, sometimes at the instigation of external stimuli but sometimes also in the absence of any apparent external influence.

Experimental psychology itself has, it is true, now and again suffered relapse into a metaphysical treatment of its problems.

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

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

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.

In Aristotle the mind, regarded as the principle of life, divides into nutrition, sensation, and faculty of thought, corresponding to the inner most important stages in the succession of vital phenomena.