Beside its thoroughgoing dependence on psychoanalytic investigation I must emphasize as a character of this work of mine its intentional independence of biological investigation. I have carefully avoided the inclusion of the results of scientific investigation in general sex biology or of particular species of animals in this study of human sexual functions which is made possible by the technique of psychoanalysis. My aim was indeed to find out how much of the biology of the sexual life of man can be discovered by means of psychological investigation; I was able to point to additions and agreements which resulted from this examination, but I did not have to become confused if the psychoanalytic methods led in some points to views and results which deviated considerably from those merely based on biology. I have added many passages in this edition, but I have abstained from calling attention to them, as in former editions, by special marks. The scientific work in our sphere has at present been retarded in its progress, nevertheless some supplements to this work were indispensable if it was to remain in touch with our newer psychoanalytic literature. VIENNA, October, 1914. I THE SEXUAL ABERRATIONS[1] The fact of sexual need in man and animal is expressed in biology by the assumption of a "sexual impulse." This impulse is made analogous to the impulse of taking nourishment, and to hunger. The sexual expression corresponding to hunger not being found colloquilly, science uses the expression "libido."[2] Popular conception makes definite assumptions concerning the nature and qualities of this sexual impulse. It is supposed to be absent during childhood and to commence about the time of and in connection with the maturing process of puberty; it is supposed that it manifests itself in irresistible attractions exerted by one sex upon the other, and that its aim is sexual union or at least such actions as would lead to union. But we have every reason to see in these assumptions a very untrustworthy picture of reality. On closer examination they are found to abound in errors, inaccuracies and hasty conclusions. If we introduce two terms and call the person from whom the sexual attraction emanates the _sexual object_, and the action towards which the impulse strives the _sexual aim_, then the scientifically examined experience shows us many deviations in reference to both sexual object and sexual aim, the relations of which to the accepted standard require thorough investigation. 1. DEVIATION IN REFERENCE TO THE SEXUAL OBJECT