The guardian-consciousness wards off, so far as it is possible, the harmful blows given by the stimuli of the external environment. In man, this same guardian consciousness keeps on constructing, by a series of elimination and selection, a new environment, individual and social, which leads to an ever higher and more perfect development and realization of the inner powers of individuality and personality. Under normal conditions man’s superior and inferior centers with their corresponding upper, critical, controlling consciousness together with the inferior automatic, reflex centers and their concomitant subconscious consciousness, keep on functioning in full harmony. The upper and lower consciousness form one organic unity,--one conscious, active personality. Under certain abnormal conditions, however, the two systems of nerve-centers with their corresponding mental activities may become dissociated. The superior nerve-centers with their critical, controlling consciousness may become inhibited, split off from the rest of the nervous system. The reflex, automatic, instinctive, subconscious centers with their mental functions are laid bare, thus becoming directly accessible to the stimuli of the outside world; they fall a prey to the influences of external surroundings, influences termed _suggestions_. The critical, controlling, guardian-consciousness, being cut off and absent, the reduced individuality lacks the rational guidance and orientation given by the upper choice- and will-centers, and becomes the helpless plaything of all sorts of suggestions, sinking into the _trance states of the subconscious. It is this subconscious that forms the highway of suggestions._ Suggestibility is the essential characteristic of the subconscious. The subconscious rises to the surface of consciousness, so to say, whenever there is a weakening, paralysis, or inhibition of the upper, controlling will and choice-centers. In other words, whenever there is a disaggregation of the superior from the inferior nerve-centers, there follows an increase of ideo-sensory, ideo-motor, sensori-secretory, reflex excitability; and ideationally, or rationally there is present an abnormal intensity of suggestibility.[6] FOOTNOTES: [5] The theory of the subconscious was first developed by me in my volume “The Psychology of Suggestion,” 1898. [6] I object to the term “Subliminal,” because it is understood in a cosmic, or metaphysical sense. The term “co-conscious” is limited and refers to independently functioning, contemporaneous personalities, or mental systems. The term “Unconscious” is _misleading_, because it may refer to the metaphysics of Hartmann. At best it simply means nervous processes which, as such, belong to neurology, physiology, but not to the domain of abnormal psychology. The term “subconscious,” used by me in “The Psychology of Suggestion,” means _tracts of mental states which may or may not function in the total mental reaction of the individual_.