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 Occult Science comes closest. Steiner even referred to it as "an epitome of anthroposophic Spiritual Science." The book systematically presents the fundamental facts concerning the nature and constitution of the human being and, chronologically, the history of the universe and humankind.
Whereas the findings of natural science are derived from observations made through the senses, the findings of Spiritual Science, or Anthroposophy, are "occult" inasmuch as they arise from direct observation of realities hidden to ordinary perception. And yet these elements of humanity and the universe form the foundation of the sense world. A substantial part of Occult Science is taken up with a description of the preliminary training needed to make such spiritual observations.