case of the child by external assistance), there is an experience of satisfaction, which puts an end to the internal excitation. An essential constituent of this experience is the appearance of a certain percept (of food in our example), the memory-image of which is henceforth associated with the memory- trace of the excitation arising from the need. Thanks to the established connection, there results, at the next occurrence of this need, a psychic impulse which seeks to revive the memory- image of the former percept, and to re-evoke the former percept itself; that is, it actually seeks to re-establish the situation of the first satisfaction. Such an impulse is what we call a wish; the reappearance of the perception constitutes the wish- fulfilment, and the full cathexis of the perception, by the excitation springing from the need, constitutes the shortest path to the wish-fulfilment. We may assume a primitive state of the psychic apparatus in which this path is actually followed, i.e., in which the wish ends in hallucination. This first psychic activity therefore aims at an identity of perception: that is, at a repetition of that perception which is connected with the satisfaction of the need.

This primitive mental activity must have been modified by bitter practical experience into a secondary and more appropriate activity. The establishment of identity of perception by the short regressive path within the apparatus does not produce the same result in another respect as follows upon cathexis of the same perception coming from without. The satisfaction does not occur, and the need continues. In order to make the internal cathexis equivalent to the external one, the former would have to be continuously sustained, just as actually happens in the hallucinatory psychoses and in hunger-phantasies, which exhaust their performance in maintaining their hold on the object desired. In order to attain to more appropriate use of the psychic energy, it becomes necessary to suspend the full regression, so that it does not proceed beyond the memory-image, and thence can seek other paths, leading ultimately to the production of the desired identity from the side of the outer world. * This inhibition, as well as the subsequent deflection of the excitation, becomes the task of a second system, which controls voluntary motility, i.e., a system whose activity first leads on to the use of motility for purposes remembered in advance. But all this complicated mental activity, which works its way from the memory-image to the production of identity of perception via the outer world, merely represents a roundabout way to wish- fulfilment made necessary by experience. *(2) Thinking is indeed nothing but a substitute for the hallucinatory wish; and if the dream is called a wish-fulfilment, this becomes something self-evident, since nothing but a wish can impel our psychic apparatus to activity. The dream, which fulfils its wishes by following the short regressive path, has thereby simply preserved for us a specimen of the primary method of operation of the psychic apparatus, which has been abandoned as inappropriate. What once prevailed in the waking state, when our psychic life was still young and inefficient, seems to have been banished into our nocturnal life; just as we still find in the nursery those discarded primitive weapons of adult humanity, the bow and arrow. Dreaming is a fragment of the superseded psychic life of the child. In the psychoses, those modes of operation of the psychic apparatus which are normally suppressed in the waking state reassert themselves, and thereupon betray their inability to satisfy our demands in the outer world. *(3)

* In other words: the introduction of a test of reality is recognized as necessary.

*(2) Le Lorrain justly extols the wish-fulfilments of dreams: "Sans fatigue serieuse, sans etre oblige de recourir a cette lutte opiniatre et longue qui use et corrode les jouissances poursuivies." [Without serious fatigue, without being obliged to have recourse to that long and stubborn struggle which exhausts and wears away pleasures sought.]

*(3) I have further elaborated this train of thought elsewhere, where I have distinguished the two principles involved as the pleasure-principle and the reality-principle. Formulations regarding the Two Principles in Mental Functioning, in Collected Papers, Vol. iv. p. 13.

The unconscious wish-impulses evidently strive to assert themselves even during the day, and the fact of transference, as well as the psychoses, tells us that they endeavour to force their way through the preconscious system to consciousness and the command of motility. Thus, in the censorship between Ucs and Pcs, which the dream forces us to assume, we must recognize and respect the guardian of our psychic health. But is it not carelessness on the part of this guardian to diminish his vigilance at night,