Now considering states in which the mental balance is disturbed, we can easily see, from what has preceded, wherein lies the importance of the unconscious for psychopathology. Let us ponder the question of where and in what manner the unconscious manifests itself in abnormal mental conditions. The way in which the unconscious works is most clearly seen in disturbances of a psychogenic nature, such as hysteria, compulsion neurosis, etc. We have known for a long time that certain symptoms of these disturbances are produced by unconscious psychic events. Just as clear, but less recognised, are the manifestations of the unconscious in actually insane patients. As the intuitive ideas of normal men do not spring from logical combinations of the conscious mind, so the hallucinations and delusions of the insane arise, not out of conscious but out of unconscious processes. Formerly, when we held a more materialistic view of psychiatry we were inclined to believe that all delusions, hallucinations, stereotypic acts, etc., were provoked by morbid processes in the brain cells. Such a theory, however, ignores that delusions, hallucinations, etc., are also to be met with in certain functional disturbances, and not only in the case of functional disturbances, but also in the case of normal people. Primitive people may have visions and hear strange voices without having their mental processes at all disturbed. To seek to ascribe symptoms of that nature directly to a disease of the brain cells I hold to be superficial and unwarranted. Hallucinations show very plainly how a part of the unconscious content can force itself across the threshold of the conscious. The same is true of a delusion whose appearance is at once strange and unexpected by the patient. The expression "mental balance" is no mere figure of speech, for its disturbance is a real disturbance of that equilibrium which actually exists between the unconscious and conscious content to a greater extent than has heretofore been recognised or understood. As a matter of fact, it amounts to this--that the normal functioning of the unconscious processes breaks through into the conscious mind in an abnormal manner, and thereby disturbs the adaptation of the individual to his environment.