Written in the form of 100 ascetic capita in the fifth century, this is a coherent treatise on the theology and anthropology of prayer. It marks a pivotal point int he development of Byzantine asceticism, discussing the use of the Jesus Prayer in the context of devotional practice which balances reason with emotion, the prayer of the intellect with the prayer of the heart. Diadochos's epistemology is therefore not only important to the history of theology; it is also a valuable contribution to current debate on the validity of spiritual experience. This new edition of the text builds upon that of Edouard des Places. The translation, introduction and commentary are based on a new and comprehensive analysis of Diadochos's theology and use of terminology. Greek and English Text in face.