Steiner's first career was academic and entirely respectable. He edited Goethe's scientific writings for the standard Weimar edition, took a doctorate in philosophy, and published The Philosophy of Freedom (1894), a work of epistemology that makes no supernatural claims at all. Only after 1900 did he begin speaking publicly about spiritual perception, and he joined the Theosophical Society's German section in 1902.
He broke with Theosophy in 1912-13 and founded Anthroposophy, and the break was substantive rather than personal: he rejected the Society's promotion of the young Jiddu Krishnamurti as the vehicle of a world teacher, and his own system is Christocentric in a way Blavatsky's is not, treating the incarnation as the pivot of cosmic history.
His claim was that the spiritual world can be investigated with the same rigour as the physical, spiritual science, and that he was reporting observations rather than speculating. That claim is not testable by the means he proposed, and it is the point on which the whole edifice turns. Helmut Zander's large historical study reads his teaching as a construction assembled from identifiable nineteenth-century sources and shaped by his audiences, which is a very different account from the movement's own.
What is beyond dispute is the practical output, which is unmatched by any other esotericist of the period: Waldorf education from 1919, biodynamic agriculture from 1924, the Camphill movement in special education, anthroposophic medicine, eurythmy, and the Goetheanum at Dornach. Hundreds of thousands of children are educated in schools founded on his ideas. The anthroposophic medical claims and the movement's historically poor stance on vaccination are the parts of that legacy under active and legitimate criticism.