Mysticism, the author points out, has been defined as that which begins with mist- and ends with- schism. However much support may be found in history for that observation, a more practical working definition would be that mysticism is a confrontation between man and the sacred. The purpose of this work is to investigate religious mysticism, in its latter definition, both theologically and comparatively. After defining his terms and explaining the basic mystical process and the structure of the mystical state, the author surveys the general lines of Christian mysticism as exhibited in the experiences and writings of St. John the Evangelist, St. Augustine of Hippo, St. Bernard, and St. John of the Cross. He then follows the same pattern for the non-Christian religions, beginning with the mysticism of ancient Egypt and continuing on through Zoroastrianism, Hinduism, Buddhism, and Confucianism. The book concludes with an appeal to the universality of mystical experience as the starting point for the achievement of ultimate religious unity among the peoples of the world. Whitson has an unusual approach to the problem of a dialogue with the non-Christian religions. He describes that approach with conviction and convincingly, in language easily intelligble to the informed layman, and his work will be of interest to those involved in the ecumenical movement as well as to those curious about the authentic mystical phenomena found in the non-Christian religious systems.