I now remember that I have a task to perform and before rising take paper and pencil, lying ready at my side, to write out the theme previously arranged in skeleton. But to my surprise I find that it cannot be recalled. To be sure, I can, by effort of will, recall individual facts, but the facts have lost their associations and meaning, they remain comparatively isolated in memory; all their correlated ramifications, their associated ideas and relations, which the night before stood out in relief and crowded into consciousness, have gone. The emotional tone and impulses which energized the thoughts have also disappeared, and with them the system of complexes as a whole. It has been dissociated, inhibited, repressed, and there is _amnesia_ for it. With the fatigue depression a new system, with different emotions and feelings, now dominates the mind and the desired system cannot be switched in. This amnesia is not one of conservation but one of reproduction; for later in the day the fatigue and depression disappear, a new energizing emotional tone arises and the sought-for system is switched in and returns in its entirety. With this change the depression system in turn disappears, and now it is difficult to recall it, excepting that as an intellectual fact I remember that such thoughts occupied my mind in the early morning hours. The two systems as a whole are distinctly differentiated from and alternate with one another. All this is only expressing in somewhat technical language a common experience, as most people, I suppose, have such _alternations of complexes_. The facts are trite enough; but, because they are of common experience, it is well to formulate them and so, as far as possible, give precision to our conception of the psychological relations which have a distinct bearing on the principles of dissociated personality and other psychoses, on character and psycho-therapeutics. When, at a later time, we take up for study the subject of dissociated personality[147] we shall find that the dissociation of consciousness sometimes takes its lines of cleavage between systems of complexes of this kind.[148] And, above all, the formation of complexes _is the foundation stone of psycho-therapeutics_.