Bishop of Photike about the middle of the fifth century. He belonged to the generation immediately after the great Greek fathers Basil and Gregory of Nazianzus, and wrote against the Arians and on the Ascension. But he is best known for his work on Christian perfection, peri gnomseoms pneumatikems. This comprises a foreword with ten definitions of virtue and one hundred Capita Gnostika, under which he attempts to analyze what it means to be Christlike and how to live such a life. He finds its basis in the three theological virtues, especially love. Diadochus was evidently a man of considerable culture which he combined with a deep faith in Christ. His work on Christian perfection enjoyed great popularity in succeeding generations and is quoted by Maximus the Confessor, in the Doctrina Patrum, and by Photius. It is still of practical value and deserves to be better known than it is.