The progress in scientific knowledge has shown its influence on the _Interpretation of Dreams_. When I wrote it in 1899 the “Sexual Theories” was not yet in existence, and the analysis of complicated forms of psychoneuroses was still in its infancy. The interpretation of dreams was destined to aid in the psychological analysis of the neuroses, but since then the deeper understanding of the neuroses has reacted on our conception of the dream. The study of dream interpretation itself has continued to develop in a direction upon which not enough stress was laid in the first edition of this book. From my own experience, as well as from the works of W. Stekel and others, I have since learned to attach a greater value to the extent and the significance of symbolism in dreams (or rather in the unconscious thinking). Thus much has accumulated in the course of this year which requires consideration. I have endeavoured to do justice to this new material by numerous insertions in the text and by the addition of footnotes. If these supplements occasionally threaten to warp the original discussion, or if, even with their aid, we have been unsuccessful in raising the original text to the _niveau_ of our present views, I must beg indulgence for the gaps in the book, as they are only consequences and indications of the present rapid development of our knowledge. I also venture to foretell in what other directions later editions of the _Interpretation of Dreams_—in case any should be demanded—will differ from the present one. They will have, on the one hand, to include selections from the rich material of poetry, myth, usage of language, and folk-lore, and, on the other hand, to treat more profoundly the relations of the dream to the neuroses and to mental diseases. Mr. Otto Rank has rendered me valuable service in the selection of the addenda and in reading the proof sheets. I am gratefully indebted to him and to many others for their contributions and corrections. VIENNA, Spring of 1911. TRANSLATOR’S PREFACE