Freud's dream theory may be summarized as follows:
1. The dream expresses a wish unsatisfied during the waking state, whether because of a conscious objection or, more frequently, because of repression, in which case the wish is unrecognized. During sleep, the psychic apparatus finds its natural tendency, which is to reduce tension, that is, to experience pleasure. The dream, like hysterical symptoms, slips, parapraxes, and so on, is a sign of the return of the repressed. Freud went further still, claiming that every dream was the fulfillment of a wish, which obviously invites an objection about unpleasurable dreams and anxiety dreams. On several occasions Freud rebutted this objection, continuing to analyze such dreams until he isolated a wish behind distress or anxiety, which he claimed were merely expressions of resistance and conflict. Truth to tell, his argument was not always persuasive. On the basis of necessarily fragmentary material, it sometimes gave an impression of the ad hoc. Freud was able to overcome this difficulty only much later, when he introduced the repetition compulsion that lay "beyond the pleasure principle" (1920g).
2. Two circumstances favor this return of the repressed. The first is the inhibition of perception and motricity during sleep, protecting the dreamer against the dangers of actual satisfaction. This results in a "topographical regression," that is, the excitation flows back unto the psyche and reinforces the dream-work. The second circumstance is that sleep weakens the censorship.
3. A measure of censorship remains, however, and often allows satisfaction of a disguised kind only. This is the function of the "dream-work." This work employs the mechanisms of condensation and displacement (primary processes) before proceeding to generate images (representability). Then, by means of secondary revision, the "dream façade" is improved to provide a plausible meaning; i.e., the manifest content of the dream, which is quite different from the underlying meaning, that of the "latent dream-thoughts." The dream work is a form of thinking, but its rules are very different from those that prevail in the logical thought of the waking state: dreams know nothing of contradiction.
4. The dream thus provides an outlet for libidinal pressure. It is the "guardian of sleep" since, without its intervention, the pressure would awaken the dreamer.
5. The dream's raw materials are "day's residues" (events, thoughts, or affects from the recent past) and physical sensations that occur during sleep. But its "real" content is reactivated infantile memories, especially those of an oedipal kind: the dream is a regression to an infantile state.
These tenets underpin dream interpretation, whose aim is to render meaningful elements in the dream's manifest content (to restore their latent meaning), on the basis of the dreamer's associations. Freud insisted that any "key to dreams," that is, any list of symbolic equivalents of supposedly general value, be excluded. He did, however, recognize some universal "symbols," transmitted by culture, and some "typical dreams" to be met with in many dreamers (dreams of nudity, for example).