In 1904, in the magazine Lucifer-Gnosis, Rudolf Steiner published some of his earliest articles on self-development, which became his classic How to Know Higher Worlds: A Modern Path of Initiation. Steiner continued his articles as "The Stages of Higher Development." He wrote of his intention in 1914: "A second part of How to Know Higher Worlds] is to be added to this first part, bringing further explanations of the frame of mind that can lead to the experience of higher worlds." Though Steiner never found time to publish those articles as a book, they are collected in...