This book is a study of the life, monastic writings, and spiritual theology of John Cassian (c., 360-435). His Institutes and Conferences are a remarkable synthesis of earlier monastic traditions, especially those of fourth-century Egypt, informed throughout by Cassian's awareness of the particular needs of the Latin monastic movement he was helping to shape. Sometimes portrayed as simply an advocate of the sophisticated spiritual theology of Evagrius of Ponticus (360-435), Cassian was actually a theologian of keen insight, realism, and creativity. His teaching on sexuality is unique in early monastic literature in both its breadth and its depth, and his integration of biblical interpretation with the ways of prayer and teaching on ecstatic prayer are of fundamental importance for the western monastic tradition. The only Latin writer included in the classic Greek collections of monastic sayings, Cassian was the major spiritual influence on both the Rule of the Master and the Rule of Benedict, as well as the source for Gregory the Great's teaching on capital sins and compunction. Columba Stewart's book is the first major study of Cassian to be published in twenty years. It begins by establishing Cassian's credibility as a teacher on the basis of his own experience as a monk and his familiarity with the fundamental literary sources. Stewart then turns to Cassian's spiritual theology, paying particular attention to Cassian's view of the monastic journey in eschatological perspective, his teaching on continence and chastity, the Christological basis of biblical interpretation and prayer, his method of unceasing prayer, and his integration of ecstatic experience with an Evagrian theology of prayer.