Whilst the procedure in which we recognize our normal ego reposes upon the desire for sleep, it appears compelled by the psycho-physiological conditions of sleep to abandon some of the energy with which it was wont during the day to keep down what was repressed. This neglect is really harmless; however much the emotions of the child’s spirit may be stirred, they find the approach to consciousness rendered difficult, and that to movement blocked in consequence of the state of sleep. The danger of their disturbing sleep must, however, be avoided. Moreover, we must admit that even in deep sleep some amount of free attention is exerted as a protection against sense-stimuli which might, perchance, make an awakening seem wiser than the continuance of sleep. Otherwise we could not explain the fact of our being always awakened by stimuli of certain quality. As the old physiologist Burdach pointed out, the mother is awakened by the whimpering of her child, the miller by the cessation of his mill, most people by gently calling out their names. This attention, thus on the alert, makes use of the internal stimuli arising from repressed desires, and fuses them into the dream, which as a compromise satisfies both procedures at the same time. The dream creates a form of psychical release for the wish which is either suppressed or formed by the aid of repression, inasmuch as it presents it as realized. The other procedure is also satisfied, since the continuance of the sleep is assured. Our ego here gladly behaves like a child; it makes the dream pictures believable, saying, as it were, “Quite right, but let me sleep.” The contempt which, once awakened, we bear the dream, and which rests upon the absurdity and apparent illogicality of the dream, is probably nothing but the reasoning of our sleeping ego on the feelings about what was repressed; with greater right it should rest upon the incompetency of this disturber of our sleep. In sleep we are now and then aware of this contempt; the dream content transcends the censorship rather too much, we think, “It’s only a dream,” and sleep on.
It is no objection to this view if there are borderlines for the dream where its function, to preserve sleep from interruption, can no longer be maintained—as in the dreams of impending dread. It is here changed for another function—to suspend the sleep at the proper time. It acts like a conscientious night-watchman, who first does his duty by quelling disturbances so as not to waken the citizen, but equally does his duty quite properly when he awakens the street should the causes of the trouble seem to him serious and himself unable to cope with them alone.