One may recognize the merits of Freud as an investigator without accepting all or even the majority of his conclusions. As the late W. H. Rivers pointed out, Freud will always be remembered in the history of psychology because he introduced new ideas and new methods into the science. Previous workers had discovered the realm of the subconscious; but they had not discovered the real nature of its relation to the rest of the mental organization. Freud pointed out that there was often a biological value attached to the power of forgetting as well as to that of remembering, and that in any case in most of us a large amount of experience is rendered unconscious by suppression, or an attempt made to force it into the unconscious by repression. He and his followers and other schools of psychologists have pointed out the importance of unresolved conflicts in determining thought and behaviour, and have made it clear that in the ordinary civilized community of to-day a large proportion of those conflicts arise out of difficulties connected with the sex-instinct. And, even if we reject the extreme claims made by many Freudians, we must admit that psycho-analysis has shown that many cases of actual perversion of instinct may be cured by analytic methods, and that sex occupies a very much larger space in the mind than was previously supposed. It had not been previously supposed, because of the fact that it tends to appear in consciousness in disguised form--either sublimated and thus intertwined with other emotions and instincts or with unusual objects, or else rationalized as something else, or kept below the surface of consciousness as an unfulfilled wish; and because there is a resistance in most of us to recognizing its importance. This revolution in our thought has proved very unpalatable to many. In just the same way as a large proportion of Darwin’s opponents opposed him because they believed that to accept man’s simian origin was a repulsive degradation, so many of the opponents of psycho-analysis oppose it because they believe that to ascribe this huge rôle to sex in the genesis of our psyche is a repulsive degradation. To my mind there are two very general questions which the student of human sex psychology now has to face, if he takes not necessarily the whole but the central theses of psycho-analysis, however much pruned, as proven. The first is this: granted that sex does play such a large part, especially in early years, in the genesis of our mental organization, is it desirable that the average adult or adolescent should, by analysis, be given full self-knowledge on the subject? The second is this: granted that sex does penetrate into more corners of mind in man than in lower organisms, is this really a regrettable thing, or can we find any grounds for believing it to be desirable or biologically progressive?