Even standing alone this statement is sufficiently striking; it is at once a theory and a challenge. But it does not stand alone. It comes at the end of many years of research among every class of mental diseases. It comes, therefore, with the authentication of experience. It is not to be lightly set aside; it claims our study; and the study of it will not go unrewarded. The short essay here translated by Dr. Eder is but an introduction to the vast field opened up by Professor Sigm. Freud and his colleagues. Already the journals of clinical psychology, normal or morbid, are full of the discussions of Professor Freud’s methods and results. There is a “Freud School.” That alone is a proof that the method is novel if not new. There are, of course, violent opponents and critical students. The opponents may provoke, but it is to the critical students that Professor Freud will prefer to speak. “The condemnation,” said Hegel, “that a great man lays upon the world is to force it to explain him.” Of a new method, either of research or of treatment—and the Freud method is both—the same may be said. It is certain that, whatever our prejudice against details may be, the theory of “psycho-analysis” and the treatment based upon it deserves, if only as a mental exercise, our critical consideration. But Professor Freud is not alone in the world of morbid psychology. Let me digress for a moment. Over twenty years ago it was my special business to study and criticise several textbooks on insanity. To the study of these textbooks I came after many years of discipline in normal psychology and the related sciences. When I came to insanity proper, I found that practically not a single textbook made any systematic effort to show how the morbid symptoms we classified as “mental diseases” had their roots in the mental processes of the normal mind. In his small book, “Sanity and Insanity,” Dr. Charles Mercier did make an effort to lay out, as it were, the institutes of insanity, the normal groundwork out of which the insanities grew, the groups of ideas that to-day serve to direct our conduct and to-morrow lose their adjustment to any but a specially adapted environment. In his later works, particularly in “Psychology, Normal and Morbid,” Dr. Mercier has followed up the central ideas of the early study. All the more recent textbooks in English contain efforts in the same direction; but with a few striking exceptions they are studies rather of physical symptoms associated with mental processes than of morbid psychology proper. It was not until there came from across the Channel Dr. Pierre Janet’s carefully elaborated studies on Hysteria that I realised what a wealth of psychological material had remained hidden in our asylums, in our nervous homes, even in our ordinary hospitals, and in the multitudes of strange cases that occur in private practice. Janet, a pupil of the Charcot School—Charcot, who made _la Salpetrière_