Binz[4] (p. 45) takes occasion from the above-mentioned characteristics of the memory in dreams to express his dissatisfaction with explanations of dreams which he himself has approved of: “And the normal dream raises similar questions. Why do we not always dream of memory impressions from the preceding days, instead of going back to the almost forgotten past lying far behind us without any perceptible reason? Why in a dream does consciousness so often revive the impression of indifferent memory pictures while the cerebral cells bearing the most sensitive records of experience remain for the most part inert and numb, unless an acute revival during the waking state has shortly before excited them?” We can readily understand how the strange preference of the dream memory for the indifferent and hence the unnoticed details of daily experience must usually lead us to overlook altogether the dependence of the dream on the waking state, or at least make it difficult to prove this dependence in any individual case. It thus happened that in the statistical treatment of her own and her friend’s dreams, Miss Whiton Calkins[12] found 11 per cent. of the entire number that showed no relation to the waking state. Hildebrandt was certainly correct in his assertion that all our dream pictures could be genetically explained if we devoted enough time and material to the tracing of their origin. To be sure, he calls this “a most tedious and thankless job.” For it would at most lead us to ferret out all kinds of quite worthless psychic material from the most remote corners of the memory chamber, and to bring to light some very indifferent moments from the remote past which were perhaps buried the next hour after their appearance. I must, however, express my regret that this discerning author refrained from following the road whose beginning looked so unpromising; it would have led him directly to the centre of the dream problem. The behaviour of the memory in dreams is surely most significant for every theory of memory in general. It teaches us that “nothing which we have once psychically possessed is ever entirely lost” (Scholz[59]); or as Delbœuf puts it, “que toute impression même la plus insignifiante, laisse une trace inaltérable, indéfiniment susceptible de reparaître au jour,” a conclusion to which we are urged by so many of the other pathological manifestations of the psychic life. Let us now bear in mind this extraordinary capability of the memory in the dream, in order to perceive vividly the contradictions which must be advanced in certain dream theories to be mentioned later, when they endeavour to explain the absurdities and incoherence of dreams through a partial forgetting of what we have known during the day.