The anthroposophy of Rudolf Steiner is not a theoretical system, but the results of research based on direct observation. As Steiner's research was so vast and conducted over such a long period of time, no single book can be said to contain the whole of his spiritual teaching. However, of all his books on occult science, also known as esoteric science, come closest. Steiner even referred to it as 'an epitome of anthroposophical spiritual science'.

Rudolf Joseph Lorenz Steiner (25 or 27 February 1861 - 30 March 1925) was an Austrian philosopher, social thinker, architect, and esotericist. He gained initial recognition as a literary critic and cultural philosopher. At the beginning of the 20th century, he founded a new spiritual movement, Anthroposophy, as an esoteric philosophy growing out of European transcendentalism and with links to Theosophy.

Originally published in 1894, Rudolf Steiner's Die Philosophie der Freiheit was considered by Steiner to be his most enduring work above all others. This is the first English translation, which was done in 1916. Two years later, in 1918, he revised it to be more in line with The Theosophical Society's philosophy. In many ways, this edition is truer to his spirit then all other translations, including some of the modern ones.  

Knowledge of the Higher Worlds and Its Attainment or How to Know the Higher Worlds is Steiner’s most essential guide to the modern path of initiation he advocated throughout his life. It has been translated into many languages and has inspired hundreds of thousands around the world. With great clarity and warmth, Rudolf Steiner details the exercises and moral qualities to be cultivated on the path to a conscious experience of supersensible realities. 

There slumber in every human being faculties by means of which he can acquire for himself a knowledge of higher worlds. Mystics, Gnostics, and Theosophists all speak of a world of soul and spirit which for them is just as real as the world we see with our physical eyes and touch with our physical hands.