further extensions and alterations when we include consideration of still other neuroses (the narcissistic) in addition to hysteria and the obsessional neurosis. In the obsessional neurosis, on the other hand, regression of the Libido to the antecedent stage of the sadistic-anal organization is the most conspicuous factor and determines the form taken by the symptoms. The impulse to love must then mask itself under the sadistic impulse. The obsessive thought, “I should like to murder you,” means (when it has been detached from certain superimposed elements that are not, however, accidental but indispensable to it) nothing else but “I should like to enjoy love of you.” When you consider in addition that regression to the primary objects has also set in at the same time, so that this impulse concerns only the nearest and most beloved persons, you can gain some idea of the horror roused in the patient by these obsessive ideas and at the same time how unaccountable they appear to his conscious perception. But repression also has its share, a great one, in the mechanism of this neurosis, and one which is not easy to expound in a rapid survey such as this. Regression of Libido without repression would never give rise to a neurosis, but would result in a perversion. You will see from this that repression is the process which distinguishes the neuroses particularly and by which they are best characterized. Perhaps, however, I may have an opportunity at some time of expounding to you what we know of the mechanism of the perversions, and you will then see that there again nothing proceeds so simply as we should like to imagine in our constructions. I think that you will be soonest reconciled to this exposition of fixation and regression of the Libido if you will regard it as preparatory to a study of the _ætiology_ of the neuroses. So far I have only given you one piece of information on this subject, namely, that people fall ill of a neurosis when the possibility of satisfaction for the Libido is removed from them—they fall ill in consequence of a ‘privation,’ as I called it, therefore—and that their symptoms are actually substitutes for the missing satisfaction. This of course does not mean that every privation in regard to libidinal satisfaction makes everyone who meets with it neurotic, but merely that in all cases of neurosis investigated the factor of privation was demonstrable. The statement therefore cannot be reversed. You will no doubt have understood that this statement was not intended to reveal the whole secret of the ætiology of the neuroses, but that it merely emphasized an important and indispensable condition.