The mechanism of dream formation is favourable in the highest degree to only one of the logical relations. This relation is that of similarity, correspondence, contiguity, “as though,” which is capable of being represented in the dream as no other can be, by the most varied expedients. The correspondences occurring in the dream, or cases of “as though,” are the chief points of support for the formation of dreams, and no inconsiderable part of the dream activity consists in creating new correspondences of this sort in cases where those which are already at hand are prevented by the censor of resistance from getting into the dream. The effort towards condensation shown by the dream activity assists in the representation of the relation of similarity. _Similarity_, _agreement_, _community_, are quite generally expressed in the dream by concentration into a _unity_, which is either already found in the dream material or is newly created. The first case may be referred to as _identification_, the second as _composition_. Identification is used where the dream is concerned with persons, composition where things are the objects of unification; but compositions are also made from persons. Localities are often treated as persons. Identification consists in giving representation in the dream content to only one of a number of persons who are connected by some common feature, while the second or the other persons seem to be suppressed as far as the dream is concerned. This one representative person in the dream enters into all the relations and situations which belong to itself or to the persons who are covered by it. In cases of composition, however, when this has to do with persons, there are already present in the dream image features which are characteristic of, but not common to, the persons in question, so that a new unity, a composite person, appears as the result of the union of these features. The composition itself may be brought about in various ways. Either the dream person bears the name of one of the persons to whom it refers—and then we know, in a manner which is quite analogous to knowledge in waking life, that this or that person is the one who is meant—while the visual features belong to another person; or the dream image itself is composed of visual features which in reality are shared by both. Instead of visual features, also, the part played by the second person may be represented by the mannerisms which are usually ascribed to him, the words which he usually speaks, or the situations in which he is usually imagined. In the latter method of characterisation the sharp distinction between identification and composition of persons begins to disappear. But it may also happen that the formation of such a mixed personality is unsuccessful. The situation of the dream is then attributed to one person, and the other—as a rule the more important one—is introduced as an inactive and unconcerned spectator. The dreamer relates something