Through the dream-work the dream process now gains either sufficient intensity to attract consciousness to itself and arouse the foreconscious, which is quite independent of the time or profundity of sleep, or, its intensity being insufficient it must wait until it meets the attention which is set in motion immediately before awakening. Most dreams seem to operate with relatively slight psychic intensities, for they wait for the awakening. This, however, explains the fact that we regularly perceive something dreamt on being suddenly aroused from a sound sleep. Here, as well as in spontaneous awakening, the first glance strikes the perception content created by the dream-work, while the next strikes the one produced from without.
But of greater theoretical interest are those dreams which are capable of waking us in the midst of sleep. We must bear in mind the expediency elsewhere universally demonstrated, and ask ourselves why the dream or the unconscious wish has the power to disturb sleep, i.e. the fulfillment of the foreconscious wish. This is probably due to certain relations of energy into which we have no insight. If we possessed such insight we should probably find that the freedom given to the dream and the expenditure of a certain amount of detached attention represent for the dream an economy in energy, keeping in view the fact that the unconscious must be held in check at night just as during the day. We know from experience that the dream, even if it interrupts sleep, repeatedly during the same night, still remains compatible with sleep. We wake up for an instant, and immediately resume our sleep. It is like driving off a fly during sleep, we awake ad hoc, and when we resume our sleep we have removed the disturbance. As demonstrated by familiar examples from the sleep of wet nurses, &c., the fulfillment of the wish to sleep is quite compatible with the retention of a certain amount of attention in a given direction.
But we must here take cognizance of an objection that is based on a better knowledge of the unconscious processes. Although we have ourselves described the unconscious wishes as always active, we have, nevertheless, asserted that they are not sufficiently strong during the day to make themselves perceptible. But when we sleep, and the unconscious wish has shown its power to form a dream, and with it to awaken the foreconscious, why, then, does this power become exhausted after the dream has been taken cognizance of? Would it not seem more probable that the dream should continually renew itself, like the troublesome fly which, when driven away, takes pleasure in returning again and again? What justifies our assertion that the dream removes the disturbance of sleep?
That the unconscious wishes always remain active is quite true. They represent paths which are passable whenever a sum of excitement makes use of them. Moreover, a remarkable peculiarity of the unconscious processes is the fact that they remain indestructible. Nothing can be brought to an end in the unconscious; nothing can cease or be forgotten. This impression is most strongly gained in the study of the neuroses, especially of hysteria. The unconscious stream of thought which leads to the discharge through an attack becomes passable again as soon as there is an accumulation of a sufficient amount of excitement. The mortification brought on thirty years ago, after having gained access to the unconscious affective source, operates during all these thirty years like a recent one. Whenever its memory is touched, it is revived and shows itself to be supplied with the excitement which is discharged in a motor attack. It is just here that the office of psychotherapy begins, its task being to bring about adjustment and forgetfulness for the unconscious processes. Indeed, the fading of memories and the flagging of affects, which we are apt to take as self-evident and to explain as a primary influence of time on the psychic memories, are in reality secondary changes brought about by painstaking work. It is the foreconscious that accomplishes this work; and the only course to be pursued by psychotherapy is the subjugate the Unc, to the domination of the Forec.