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V. THE SPECIAL CHARACTERISTICS OF THE SYSTEM Ucs.

The distinction we have made between the two psychical systems receives fresh significance when we observe that processes in the one system, the Ucs., show characteristics which are not met with again in the system immediately above it.

The nucleus of the Ucs. consists of instinctual representatives which seek to discharge their cathexis; that is to say, it consists of wishful impulses. These instinctual impulses are co-ordinate with one another, exist side by side without being influenced by one another, and are exempt from mutual contradiction. When two wishful impulses whose aims must appear to us incompatible become simultaneously active, the two impulses do not diminish each other or cancel each other out, but combine to form an intermediate aim, a compromise.

There are in this system no negation, no doubt, no degrees of certainty: all this is only introduced by the work of the censorship between the Ucs. and the Pcs. Negation is a substitute, at a higher level, for repression. In the Ucs. there are only contents, cathected with greater or lesser strength.

The cathectic intensities are much more mobile. By the process of displacement one idea may surrender to another its whole quota of cathexis; by the process of condensation it may appropriate the whole cathexis of several other ideas. I have proposed to regard these two processes as distinguishing marks of the so-called primary psychical process. In the system Pcs. the secondary process¹ is dominant. When a primary process is allowed to take its course in connection with elements belonging to the system Pcs., it appears ‘comic’ and excites laughter.

¹ Cf. the discussion in Chapter VII of The Interpretation of Dreams (1900a), based on ideas developed by Breuer in Studies on Hysteria (Breuer and Freud, 1895).