Two books, published in 1902 and 1911, continue to shape our understanding of mysticism today. William James’s landmark study The Varieties of Religious Experience: A Study in Human Nature, published in 1902, elevated him to a leading authority on the study of religious experience. This detailed phenomenological study focused on conversion and the value of saintliness, but James also devoted 123 pages to his analysis of mysticism (including his oft-cited four marks of mystical experience) and mysticism’s relationship to theology, psychology, symbolism and magic. While James’s work was acclaimed, Evelyn Underhill dismissed it, feeling that James had misunderstood the nature of mysticism and the subsequent path, the mystic way. She responded by writing Mysticism: A Study in the Nature and Development of Man’s Spiritual Consciousness. This paper undertakes an examination and comparison of these two towering figures’ understandings of the nature of mysticism, framed through the lens of their methodology.