I would warn those of you, however, who care to continue, that my two assumptions are not of equal worth. The first, that the dream is a psychic phenomenon, is the assumption we wish to prove by the results of our work. The other has already been proved in another field, and I take the liberty only of transferring it from that field to our problem. Where, in what field of observation shall we seek the proof that there is in man a knowledge of which he is not conscious, as we here wish to assume in the case of the dreamer? That would be a remarkable, a surprising fact, one which would change our understanding of the psychic life, and which would have no need to hide itself. To name it would be to destroy it, and yet it pretends to be something real, a contradiction in terms. Nor does it hide itself. It is no result of the fact itself that we are ignorant of its existence and have not troubled sufficiently about it. That is just as little our fault as the fact that all these psychological problems are condemned by persons who have kept away from all observations and experiments which are decisive in this respect. The proof appeared in the field of hypnotic phenomena. When, in the year 1889, I was a witness to the extraordinarily enlightening demonstrations of Siebault and Bernheim in Nancy, I witnessed also the following experiment: If one placed a man in the somnambulistic state, allowed him to have all manner of hallucinatory experience, and then woke him up, it appeared in the first instance that he knew nothing about what had happened during his hypnotic sleep. Bernheim then directly invited him to relate what had happened to him during the hypnosis. He maintained he was unable to recall anything. But Bernheim insisted, he persisted, he assured him he did know, that he must recall, and, incredible though it may seem, the man wavered, began to rack his memory, recalled in a shadowy way first one of the suggested experiences, then another; the recollection became more and more complete and finally was brought forth without a gap. The fact that he had this knowledge finally, and that he had had no experiences from any other source in the meantime, permits the conclusion that he knew of these recollections in the beginning. They were merely inaccessible, he did not know that he knew them; he believed he did not know them. This is exactly what we suspect in the dreamer.