Fichte's concept of the ego, submitted to Heinrich von Stein, whose "Seven Books of Platonism" Steiner esteemed. Steiner's dissertation was later published in expanded form as "Truth and Knowledge: Prelude to a Philosophy of Freedom", with a dedication to Eduard von Hartmann. Two years later, in 1894, he published "Die Philosophie der Freiheit" (The Philosophy of Freedom "or" The Philosophy of Spiritual Activity, the latter being Steiner's preferred English title), an exploration of epistemology and ethics that suggested a way for humans to become spiritually free beings. Steiner later spoke of this book as containing implicitly, in philosophical form, the entire content of what he later developed explicitly as anthroposophy.