Ladies and gentlemen, what attitude are we to assume to these unusual varieties of sex gratification? Nothing at all is achieved by the mere expression of indignation and personal disgust and by the assurance that we do not share these lusts. That is not our concern. We have here a field of observation like any other. Moreover, the evasion that these persons are merely rarities, curiosities, is easily refuted. On the contrary, we are dealing with very frequent and widespread phenomena. If, however, we are told that we must not permit them to influence our views on sexual life, since they are all aberrations of the sexual instinct, we must meet this with a serious answer. If we fail to understand these abnormal manifestations of sexuality and are unable to relate them to the normal sexual life, then we cannot understand normal sexuality. It is, in short, our unavoidable task to account theoretically for all the potentialities of the perversions we have gone over and to explain their relation to the so-called normal sexuality. A penetrating insight due to Ivan Bloch and two new experimental results will help us in this task. Bloch takes exception to the point of view which sees in a perversion a "sign of degeneration"; he proves that such deviations from the aim of the sexual instinct, such loose relations to the object of sexuality, have occurred at all times, among the most primitive and the most highly civilized peoples, and have occasionally achieved toleration and general recognition. The two experimental results were obtained in the course of psychoanalytic investigations of neurotics; they will undoubtedly exert a decided influence on our conceptions of sexual perversion.