But the contrast of masochism and sadism may also be used to invalidate the assumption that the former has its origin in the reflex effect of passive flagellation; and that all the rest is the product of associations of related ideas, as Binet, in explanation of Rousseau’s case, thinks, and as Rousseau himself believed. In the active maltreatment forming the object of the sadist’s sexual desire there is, in fact, no irritation of his own sensory nerves by the act of maltreatment; so that there can be no doubt of the purely psychical character of the origin of this perversion. Sadism and masochism, however, are so related to each other, and so correspond in all points with each other, that the one allows, by analogy, a conclusion for the other; and this is alone sufficient to establish the purely psychical character of masochism. According to the above-detailed contrast of all the elements and phenomena of masochism and sadism, and as a _résumé_ of all observed cases, lust in the infliction of pain and lust in inflicted pain appear but as two different sides of the same psychical process, of which the primary and essential thing is the consciousness of active or passive subjection, in which the combination of cruelty and lustful pleasure has only a secondary psychological significance. Acts of cruelty serve to express this subjection; first, because they are the most extreme means for the expression of this relation; and, again, because they represent the most intense effect that one person, either with or without coitus, can exert on another. The cases in which sadism and masochism occur simultaneously in one individual are interesting, but they present some difficulties of explanation. Cases 49, 50, 58, etc., are of this kind, and also particularly Case 30. From the latter it is evident that it is especially the idea of subjection that, both actively and passively, forms the nucleus of the perverse desires. Traces of the same thing are also to be observed, with more or less clearness, in many other cases. At any rate, one of the two perversions is always markedly predominant. Owing to this marked predominance of one perversion, and the later appearance of the other, in such cases it may well be assumed that the predominating perversion is _original_, and that the other has been _acquired_ in the course of time. The ideas of subjection and maltreatment, colored with lustful pleasure, either in an active or passive sense, have become deeply impressed in such an individual. Occasionally the imagination is tempted to try the same ideas in an inverted _rôle_. There may even be realization of this inversion. Such attempts in imagination and in acts, however, are usually soon abandoned as inadequate for the original inclination.