The process of arriving at an object, which plays an important part in mental life, takes place alongside of the organization of the libido. After the stage of auto-erotism, the first love-object in the case of both sexes is the mother; and it seems probable that, to begin with, the child does not distinguish its mother’s organ of nutrition from its own body. Later, but still in the first years of infancy, the relation known as the Œdipus complex, becomes established: boys concentrate their sexual wishes upon their mother and develop hostile impulses against their father as being a rival, while girls develop an analogous attitude. All of the different variations and consequences of the Œdipus complex are important; and in particular the innately bisexual constitution of human beings makes itself felt and increases the number of simultaneously active tendencies. Children do not become clear for quite a long time upon the differences between the sexes; and during this period of _sexual enquiry_ they produce typical _sexual theories_ which, since they are limited by the incompleteness of their authors’ own physical development, are a mixture of truth and error and fail to solve the problems of sexual life (the riddle of the Sphinx, the question of where babies come from). We see, then, that a child’s first object-choice is an _incestuous_ one. The whole course of development that I have described is run through rapidly. For the most remarkable feature of the sexual life of man is that it comes on in two waves, with an interval between them. It reaches a first climax in the fourth or fifth year of a child’s life. But this early growth of sexuality is nipped in the bud; the sexual impulses, which have shown such liveliness, are overcome by repression, and a _period of latency_ follows, which lasts until puberty and during which the “reaction-formations” of morality, shame and disgust are built up. Of all living creatures, man alone seems to show this double onset of sexual growth, and it may perhaps be the biological determinant of his predisposition to neuroses. At puberty the impulses and object-relations of a child’s early years become re-animated, and amongst them the emotional ties of his Œdipus complex. The sexual life of puberty is a struggle between the impulses of early years and the inhibitions of the latency period. Before this, and while the child is at the highest point of its infantile sexual development, a genital organization of a sort is established; but only the _male_ genitals play a part in it, and the female ones remain undiscovered. (I have described this as the period of _phallic_ primacy.) At this stage the contrast between the sexes is not stated in terms of “male” or “female” but of “possessing a penis” or “castrated.” The _castration complex_ which arises in this connexion is of the profoundest importance in the formation alike of character and of neuroses.