The Key to Theosophy is an 1889 book by Helena Blavatsky, expounding the principles of theosophy in a readable question-and-answer manner. It covers Theosophy and the Theosophical Society, Nature of the Human Being, Life After Death, Reincarnation, Kama-Loka and Devachan, the Human Mind, Practical Theosophy and the Mahatmas. The book is an introduction to Theosophical mysticism and esoteric doctrine.