There are other sources of psychological knowledge, which become accessible at the very point where the experimental method fails us.

Thus ordered thinking arises out of the ordered course of nature in which man finds himself, and this thinking is from the beginning nothing more than the subjective reproduction of the regularity according to the law of natural phenomena. On the other hand, this reproduction is only possible by means of the will that controls the concatenation of ideas.

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.

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.

Some say that everything that is called a psychical law is nothing but the psychological reflex of physical combinations, which is made up of sensations joined to certain central cerebral processes... It is contradicted by the fact of consciousness itself, which cannot possibly be derived from any physical qualities of material molecules or atoms.

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

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.