"In my book How to Know Higher Worlds, the path to higher knowledge has been traced up to the meeting with the two Guardians of the Threshold. The relation in which the soul stands to the different worlds as it passes through the successive stages of knowledge will now be described. What will be given may be called 'the teachings of esoteric science.'" -- Rudolf Steiner (chapter 1) In 1904, in the magazine Lucifer-Gnosis, ...