Plato put on the portals of his academy the inscription, "No one can enter here without a knowledge of geometry." Similarly no one can gain access to the facts of abnormal psychology without a thorough understanding of the subconscious. The subconscious may be briefly defined as mental processes of which the individual is not directly conscious. Such knowledge is all the more requisite as psychopathic disturbances with which psychopathology proper deals are essentially affections of subconscious life activity. The general drift of my Psychology of Suggestion is the description of the subconscious as a diffused consciousness below the margin of personal consciousness. I sometimes use the term "subconscious self." I designate by "self" not personal consciousness, but mere consciousness. In Multiple Personality, in which I develop the theory of thresholds in regard to the phenomena of normal and abnormal mental life, I define the subconscious as consciousness below the threshold of attentive personal consciousness. I find that my clinical and psychological investigations more and more confirm me in the view of the subconscious advanced by me in The Psychology of Suggestion. I am pleased to find that Prof. James, in a recent article, accepts the same view, and advances the same theory of threshold in regard to the subconscious. "Nobody knows," he writes, "how far we are 'marginally' conscious of these memories, concepts and conational states at ordinary times, or how far beyond the 'margin' of our present thought trans-marginal consciousness of them may exist."
In my Psychology of Suggestion I pointed out the difficulties of the purely physiological interpretation of the subconscious. Since this view still lingers among some psychologists, I cannot do better than reproduce the passage: "The facts of hypnotic memory alone strongly indicate the intelligent nature of the subconscious. Can the theory of unconscious cerebration explain, for instance, the fact of suggested amnesia during hypnosis? I hypnotize Mr. V. F. and make him pass through many lively scenes and actions. I give him hypnotic and post-hypnotic suggestions. The subject is wakened and hypnotized time and again. At last he is put into a hypnotic state, and it is suggested that on awakening he shall not remember anything of what had happened in the state of hypnosis. The subject, on emerging from his trance, remembers nothing of what he has passed through. I then put my hand on his forehead and tell him in a commanding voice, 'You remember now everything.' As if touched by the wand of a magician, the suppressed memories become endowed with life and movement, and invade the consciousness of the subject. Everything is now clearly remembered, and the subject is able to relate the tale of his adventures without the omission of the least incident. So detailed is the account that one cannot help wondering at the extraordinary memory displayed by the subject.
How is the theory of unconscious cerebration to account for this strange fact? Prof. Ziehen, in his Physiological Psychology tells us that "it is still a matter of doubt whether, despite their complication, all the acts of the hypnotized individual are not motions accomplished without any concomitant psychical processes," and that "even the recollection of the hypnotic psychical processes do not necessarily argue in favor of their existence during the hypnotic trance." This extreme view is certainly wrong, for the subject during hypnosis not only acts, moves, but he also speaks, answers questions intelligently, reasons, discusses; and if such an individual may be regarded as a mere machine, on the same grounds we may consider any rational man as a mere unconscious automaton.