What provoked the dream in the example which we have analyzed? The really unimportant event, that a friend invited me to a free ride in his cab. The table d’hôte scene in the dream contains an allusion to this indifferent motive, for in conversation I had brought the taxi parallel with the table d’hôte. But I can indicate the important event which has as its substitute the trivial one. A few days before I had disbursed a large sum of money for a member of my family who is very dear to me. Small wonder, says the dream thought, if this person is grateful to me for this—this love is not cost-free. But love that shall cost nothing is one of the prime thoughts of the dream. The fact that shortly before this I had had several drives with the relative in question puts the one drive with my friend in a position to recall the connection with the other person. The indifferent impression which, by such ramifications, provokes the dream is subservient to another condition which is not true of the real source of the dream—the impression must be a recent one, everything arising from the day of the dream.
I cannot leave the question of dream displacement without the consideration of a remarkable process in the formation of dreams in which condensation and displacement work together towards one end. In condensation we have already considered the case where two conceptions in the dream having something in common, some point of contact, are replaced in the dream content by a mixed image, where the distinct germ corresponds to what is common, and the indistinct secondary modifications to what is distinctive. If displacement is added to condensation, there is no formation of a mixed image, but a common mean which bears the same relationship to the individual elements as does the resultant in the parallelogram of forces to its components. In one of my dreams, for instance, there is talk of an injection with propyl. On first analysis I discovered an indifferent but true incident where amyl played a part as the excitant of the dream. I cannot yet vindicate the exchange of amyl for propyl. To the round of ideas of the same dream, however, there belongs the recollection of my first visit to Munich, when the Propylœa struck me. The attendant circumstances of the analysis render it admissible that the influence of this second group of conceptions caused the displacement of amyl to propyl. Propyl is, so to say, the mean idea between amyl and propylœa; it got into the dream as a kind of compromise by simultaneous condensation and displacement.
The need of discovering some motive for this bewildering work of the dream is even more called for in the case of displacement than in condensation.