It is surely a significant manifestation of the permanence of the soul's quest for God that the Western world, at a time when human values, principles, and ideals are being questioned and rejected, has turned to an interest in the age-old practice of the East - the quest for inner peace and tranquility as found in the profoundly moving experience of contemplation after the method of Zen Buddhism. In this deeply sympathetic study, the author compares the principles and practices of Zen with the traditional concepts, aims, and results of Christian mysticism. His object is, first, ecumenical - to explore the bases of Zen and Christian mysticism, so the Buddhist and Christian can communicate; second, to rethink the basic concepts of Catholic mystical theology in the light of the Zen experience; and last, to encourage more people to contemplative prayer.