The work comprises two volumes—under the respective sub-titles “Form and Reality” and “World-historical Perspectives”—of which the present translation covers the first only. Some day I hope to have the opportunity of completing a task which becomes—such is the nature of this book—more attractive in proportion to its difficulty. References to Volume II are, for the present, necessarily to the pages of the German original; if, as is hoped, this translation is completed later by the issue of the second volume, a list of the necessary adjustments of page references will be issued with it. The reader will notice that translator’s foot-notes are scattered fairly freely over the pages of this edition. In most cases these have no pretensions to being critical annotations. They are merely meant to help the reader to follow up in more detail the points of fact which Spengler, with his “ständig präsentes Wissen,” sweeps along in his course. This being their object, they take the form, in the majority of cases, of references to appropriate articles in the Encyclopædia Britannica, which is the only single work that both contains reasonably full information on the varied (and often abstruse) matters alluded to, and is likely to be accessible wherever this book may penetrate. Every reader no doubt will find these notes, where they appertain to his own special subject, trivial and even annoying, but it is thought that, for example, an explanation of the mathematical Limit may be helpful to a student who knows all about the Katharsis in Greek drama, and _vice versa_. In conclusion I cannot omit to put on record the part that my wife, Hannah Waller Atkinson, has taken in the work of translation and editing. I may best describe it by saying that it ought perhaps to have been recorded on the title page instead of in this place. C. F. A. _January, 1926._ PREFACE TO THE REVISED EDITION At the close of an undertaking which, from the first brief sketch to the final shaping of a complete work of quite unforeseen dimensions, has spread itself over ten years, it will not be out of place to glance back at what I intended and what I have achieved, my standpoint then and my standpoint to-day. In the Introduction to the 1918 edition—inwardly and outwardly a fragment—I stated my conviction that an idea had now been irrefutably formulated which no one would oppose, once the idea had been put into words. I ought to have said: once that idea had been understood. And for that we must look—as I more and more realize—not only in this instance but in the whole history of thought—to the new generation that is _born_ with the ability to do it.