But to Case, sexuality became an increasingly important subject. In his "Book of Tokens", a collection of inspired meditations on the 22 Tarot Keys of the Major Arcana, Case comments on the sex function, "You must wholly alter your conception of sex in order to comprehend the Ancient Wisdom. It is the interior nervous organism, not the external organs, that is always meant in phallic symbolism, and the force that works through these interior centers is the Great Magical Agent, the divine serpent fire." In his works, "The True and Invisible Rosicrucian Order" and "The Masonic Letter G", he writes of certain practices involving the redirection of the sexual force to the higher centers of the brain where experience of supersensory states of consciousness becomes possible.