1073

The indifferent impression which becomes a dream-instigator owing to associations of this kind is subject to a further condition which does not apply to the true source of the dream: it must always be a recent impression, derived from the dream-day.

I cannot leave the subject of dream-displacement without drawing attention to a remarkable process which occurs in the formation of dreams and in which condensation and displacement combine to produce the result. In considering condensation we have already seen the way in which two ideas in the dream-thoughts which have something in common, some point of contact, are replaced in the dream-content by a composite idea, in which a relatively distinct nucleus represents what they have in common, while indistinct subordinate details correspond to the respects in which they differ from each other. If displacement takes place in addition to condensation, what is constructed is not a composite idea but an ‘intermediate common entity’, which stands in a relation to the two different elements similar to that in which the resultant in a parallelogram of forces stands to its components. For instance, in the content of one of my dreams there was a question of an injection with propyl. To begin with, the analysis only led me to an indifferent experience which had acted as dream-instigator, and in which a part was played by amyl. I was not yet able to justify the confusion between amyl and propyl . In the group of ideas behind this same dream, however, there was also a recollection of my first visit to Munich, where I had been struck by the Propylaea. The details of the analysis made it plausible to suppose that it was the influence of this second group of ideas upon the first one that was responsible for the displacement from amyl to propyl. Propyl is as it were an intermediate idea between amyl and Propylaea, and found its way into the content of the dream as a kind of compromise, by means of simultaneous condensation and displacement.

There is a still more urgent necessity in the case of the process of displacement than in that of condensation to discover the motive for these puzzling efforts on the part of the dream-work.