Conceptions of great importance do not arise only in one brain, but are floating in the air and dip here and there, appearing even under other forms, and in other regions, where it is often very difficult to recognize the common fundamental idea. Thus it happened with the splitting up of sexuality into the polymorphic perverse sexuality of childhood. Experience forces us to accept a constant exchange of isolated components as we notice more and more that, for instance, perversities exist at the expense of normal sexuality, or that the increase of certain kinds of sex-manifestations causes corresponding deficiencies of another kind. To make the matter clearer, let me give you an instance: A young man had a homo-sexual phase lasting for some years, during which time women had no interest for him. This abnormal condition changed gradually toward his twentieth year and his erotic interest became more and more normal. He began to take great interest in girls, and soon the last traces of his homo-sexuality were conquered. This condition lasted several years, and he had some successful love-affairs. Then he wished to get married; he had here to suffer a great disappointment, as the girl to whom he proposed refused him. During the ensuing phase he absolutely abandoned the idea of marriage. After that he experienced a dislike of all women, and one day he discovered that he was again perfectly homo-sexual, that is, young men had an unusually irritating influence upon him. To regard sexuality as composed of a fixed hetero-sexual component, and a like homo-sexual element, will never suffice to explain this case, for the conception of the existence of fixed components excludes any kind of transformation. To understand the case, we have to admit a great mobility of the sexual components, which even goes so far that one of the components can practically disappear completely, whilst the other comes to the front. If only substitution took place, if for instance the homo-sexual component entered the unconscious, leaving the field of consciousness to the hetero-sexual component, modern scientific knowledge would lead us to conclude that equivalent effects arose from the unconscious sphere. Those effects would have to be conceived as resistances against the activity of the hetero-sexual component, as a repugnance towards women.