I did not have the feeling that I was writing a “centennial book” to mark the beginning of the century when I set about to outline the World and Life Conceptions of the Nineteenth Century, which appeared in 1901. The invitation to present this book as a contribution to a collection of philosophical works only provided me with the challenge to sum up results of the philosophical developments since the age of Kant, at which I had arrived long ago, and which I had meant to publish. When a new edition of the book became necessary and when I reexamined its content, I became aware of the fact that only through a considerable enlargement of the account as it was originally given could I make completely clear what I had intended to show. I had at that time limited myself to the characterization of the last one hundred and thirty years of philosophical development. Such a limitation is justifiable because this period indeed constitutes a well-rounded totality that is closed in itself and could be portrayed as such even if one did not mean to write a “centennial book.” But the philosophical views of the last century lived within me in such a way that, in presenting its philosophical problems, I felt resounding as undertones in my soul the solutions that had been attempted since the beginning of the course of the history of philosophy. This sensation appeared with greater intensity as I took up the revision of the book for a new edition. This indicates the reason why the result was not so much a new edition but a new book.
To be sure, the content of the old book has essentially been preserved word for word, but it has been introduced by a short account of the philosophical development since the sixth century B.C. In the second volume the characterization of the successive philosophies will be continued to the present time. Moreover, the short remarks at the end of the second volume entitled, Outlook, have been extended into a detailed presentation of the philosophical possibilities of the present. Objections may be raised against the composition of the book because the parts of the earlier version have not been shortened, whereas the characterization of the philosophies from the sixth century B.C. to the nineteenth century A.D. has only been given in the shortest outline. But since my aim is to give not only a short outline of the history of philosophical problems but to discuss these problems and the attempt at their solution themselves through their historical treatment, I considered it correct to retain the more detailed account for the last period. The way of approach in which these questions were seen and presented by the philosophers of the nineteenth century is still close to the trends of thought and philosophical needs of our time. What precedes this period is of the same significance to modern soul life only insofar as it spreads light over the last time interval. The Outlook at the end of the second volume had its origin in the same intention, namely, that of developing through the account of the history of philosophy, philosophy itself.
The reader will miss some things in this book that he might look for in a history of philosophy — the views of Hobbes and others, for instance. My aim, however, was not to enumerate all philosophical opinions, but to present the course of development of the philosophical problems. In such a presentation it is inappropriate to record a philosophical opinion of the past if its essential points have been characterized in another connection.
Whoever wants to find also in this book a new proof that I have “changed” my views in the course of years will probably not even then be dissuaded from such an “opinion” if I point out to him that the presentation of the philosophical views that I gave in the World and Life Conceptions has, to be sure, been enlarged and supplemented, but that the content of the former book has been taken over into the new one in all essential points, literally unchanged. The slight changes that occur in a few passages seemed to be necessary to me, not because I felt the need after fifteen years of presenting some points differently, but because I found that a changed mode of expression was required by the more comprehensive connection in which here and there a thought appears in the new book, whereas in the old one such a connection was not given. There will, however, always be people who like to construe contradictions among the successive writings of a person, because they either cannot or else do not wish to consider the certainly admissible extension of such a person's thought development. The fact that in such an extension much is expressed differently in later years certainly cannot constitute a contradiction if one does not mean by consistency that the latter expression should be a mere copy of the earlier one, but is ready to observe a consistent development of a person. In order to avoid the verdict of “change of view” of critics who do not consider this fact, one would have to reiterate, when it is a question of thoughts, the same words over and over again.