The spheres of life are many and for each there develops a special science. But life itself is one, and the more the sciences strive to penetrate deeply into their separate spheres, the more they withdraw themselves from the vision of the world as a living whole. There must be one supreme science which seeks in the separate sciences the elements for leading men back once more to the fullness of life. The scientific specialist seeks in his studies to gain a knowledge of the world and its workings. This book has a philosophical aim: science itself is here infused with the life of an organic whole. The special sciences are stages on the way to this all-inclusive science. A similar relation is found in the arts. The composer in his work employs the rules of the theory of composition. This latter is an accumulation of principles, knowledge of which is a necessary presupposition for composing. In the act of composing, the rules of theory become the servants of life, of reality. In exactly the same way philosophy is an art. All genuine philosophers have been artists in concepts. Human ideas have been the medium of their art, and scientific method their artistic technique. Abstract thinking thus gains concrete individual life. Ideas turn into life-forces. We have no longer merely a knowledge about things, but we have now made knowledge a real, self-determining organism. Our consciousness, alive and active, has risen beyond a mere passive reception of truths. How philosophy, as an art, is related to freedom; what freedom is; and whether we do, or can, participate in it--these are the principal problems of my book. All other scientific discussions are put in only because they ultimately throw light on these questions which are, in my opinion, the most intimate that concern mankind. These pages offer a "Philosophy of Freedom." All science would be nothing but the satisfaction of idle curiosity did it not strive to enhance the existential value of human personality. The true value of the sciences is seen only when we are shown the importance of their results for humanity. The final aim of an individuality can never be the cultivation of any single faculty, but only the development of all capacities which slumber within us. Knowledge has value only in so far as it contributes to the all-round unfolding of the whole nature of man. This book, therefore, does not conceive the relation between science and life in such a way that man must bow down before the world of ideas and devote his powers to its service. On the contrary, it shows that he takes possession of the world of ideas in order to use them for his human aims, which transcend those of mere science. Man must confront ideas as master, lest he become their slave. APPENDIX III PREFACE TO THE ORIGINAL EDITION OF "TRUTH AND SCIENCE"