This work, essentially Rudolf Steiner`s doctoral dissertation, subtitled "Introduction to the Philosophy of Freedom," is just that an essential work in the foundations of spiritual science. In it, the epistemological foundations of spiritual knowledge are clearly and logically presented.Originally published with The Philosophy of Freedom in a single volume, this work is fundamental to an understanding of that work (currently published as Intuitive Thinking As a Spiritual Path) and to a more complete comprehension of the philosophical basis of Steiner`s spiritual science.