This is a very important and unusual lecture, for a number of reasons. Steiner gave very few presentations at academic conferences; indeed, this may be the only one he gave after becoming the head of the Theosophical Society in Germany. He took great care in preparing it, and was proud of it afterwards. He refers to it, or to the arguments it contains, often, and it is one of the cornerstones of what I would like to term Rudolf Steiner's "late philosophy."