The following pages are a translation of Dr. Steiner's Philosophie der Freiheit, which was published in Germany some twenty years ago. The edition was soon exhausted, and has never been reprinted; copies are much sought after but very difficult to obtain. The popularity of Dr. Steiner's later works upon ethics, mysticism, and kindred subjects has caused people to forget his earlier work upon philosophy in spite of the fact that he makes frequent references to this book and it contains the germs of which many of his present views are the logical outcome. For the above reasons, and with the author's sanction, I have decided to publish a translation. In 1918 Dr. Steiner published a revised edition of the Philosophie der Freiheit. For the translation of the new passages added to, and of the incidental changes made in, this revised edition I am indebted to Mr. Hoernlé, now Professor of Philosophy in the Armstrong College (Newcastle-upon-Tyne), University of Durham. At the author's request I have changed the title to Philosophy of Spiritual Activity, and throughout the entire work "freedom" should be taken to mean "spiritual activity." Dr. Steiner's Ph. D. Thesis on "Truth and Science," originally published as a prelude to The Philosophy of Freedom, has, with his consent, been translated for this edition and been added at the end of this volume.