A work, such as the present one which opens up new paths for research and which, even when it revives old trends and theories, still substantially transvaluates them, should have had at its appearance a mediating introduction; a preface or an introductory chapter ought to have prepared the reader historically and topically and ought to have warned him of all of the misinterpretations which were suggested by the prevailing trends of thought. In this way the understanding of the uniqueness of the thoughts communicated and, hence, of their proper effect would surely have been promoted. I was keenly aware of this desideratum at the first edition of this work, but I was incapable of fulfilling it. There is, after all, a great difference between performing novel theoretical discoveries out of innermost necessity and in pure dedication to the demands of the subject matter on the one hand and one's being clear in reflection on the unique sense and scope of these discoveries — or rather, on the unique sense of the method employed — on the other.