=The meanings of the unconscious, subconscious, and coconscious.=—Though the term “unconscious” is in general use it has so many connotations derived from its various meanings in metaphysics, psychology, and physiology that its use has given rise to considerable confusion of thought, particularly, I am compelled to believe, in the interpretation of specific psycho-physiological phenomena. Nevertheless, it has been so well established in our nomenclature that we could not replace it if we would. Nor is it wholly desirable to do so. It is a good and useful term, but I believe that with each advance in the precision of our knowledge we ought, so far as accumulative data permit, to give precision to the concept for which it stands. Just as in physical science we attempt to give precision to our concept of electricity in conformity with new data accumulated from time to time, so our psychological concepts should be defined and limited in accordance with the advance in knowledge. Some do not like to define the term, not being quite willing to commit themselves unreservedly to the complete acceptance of the physiological theory of memory and to cut adrift from the metaphysical concept of a subliminal mind. If the psycho-physiological theory of memory, which is now generally accepted, is sound, we have one meaning of the unconscious which is a very definite concept, namely, the brain residua, physiological “dispositions” or neurograms in which the experiences of life are conserved. These terms become, therefore, synonyms for the unconscious. That, under certain conditions, the passive neurograms may, under stimulation, become active and function unconsciously (i.e., without corresponding psychological equivalents being introduced into the personal consciousness), need not invalidate the concept. We are then dealing with an unconscious and dynamic process. The effects of such functioning are simply the manifestations of the unconscious and may be recognized either in modifications of the stream of consciousness or in bodily disturbances. The term unconscious is an appropriate and descriptive term to characterize that which is devoid of the attributes of consciousness. This use of the term has been sanctioned by common usage.