It is not any more accurate to say that psycho-analysis has not occupied itself at all with the non-sexual side of the personality. The very distinction between the Ego and sexuality has shown us with particular clearness that the Ego-instincts also undergo an important development which is neither entirely independent of the development of the Libido nor without influence upon the latter. We certainly understand the development of the Ego much less well than the development of the Libido, because it is only by the study of the narcissistic neuroses that we have just reached some hope of insight into the structure of the Ego. Nevertheless, we have already a notable attempt on the part of Ferenczi[48] to reconstruct theoretically the developmental stages of the Ego; and there are at least two points at which we have a secure foothold from which to examine this development further. We are not at all disposed to think that the libidinal interests of a human being are from the outset in opposition to the interests of self-preservation; the Ego is rather impelled at every stage to attempt to remain in harmony with the corresponding stage of sexual organization and to accommodate itself to that. The succession of the separate phases in the development of the Libido probably follows a prescribed course; it is undeniable, however, that this course may be influenced from the direction of the Ego. A certain parallelism, a definite correspondence between the phases in the two developments (of the Ego and of the Libido) may also be assumed; indeed, a disturbance in this correspondence may become a pathogenic factor. More important to us is the question how the Ego behaves when the Libido has undergone a powerful fixation at an earlier point in its development. The Ego may countenance the fixation and will then be perverse to that extent, or, what is the same thing, infantile; it may, however, hold itself averse from this attachment of Libido, the result of which is that where the Libido undergoes a _fixation_ there the Ego institutes an act of _repression_. In this way we arrive at the conclusion that the third factor in the ætiology of the neuroses, the susceptibility to conflict, is as much connected with the development of the Ego as with the development of the Libido; our insight into the causation of the neuroses is thus enlarged. First, there is the most general condition of privation, then the fixation of Libido (forcing it into particular channels), and thirdly, the _susceptibility to conflict_ produced by the development of the Ego having repudiated libidinal excitations of that particular kind. The thing is therefore not so very obscure and intricate—as you probably thought it during the course of my exposition. To be sure, though, after all, we have not done with it yet; there is still something new to add and something we already know to dissect further.