By Fr. George Florovsky
The blessed Diadochus, bishop of Photice in ancient Epirus, stands apart in the ranks of ascetic authors. The only thing we know of him is that he was bishop in the mid-fifth century — his signature is on a letter to the Emperor Leo, a letter by the bishops of Epirus after the murder of Proterius of Alexandria by the Monophysites in 457. Contemporary historians do not mention him. St. Photius says nothing about his life but does refer to his "outstanding" address and mentions him as one of the opponents of the Monophysites at the time of the Council of Chalcedon in 451 (Bibl. cod. 231).
Diadochus' works enjoyed a wide circulation — there are numerous manuscript copies which are frequently referred to by others, and excerpts from them were taken for anthologies and florilegiae. His most important work is the Capita centum de perfectione spirituali — One Hundred Chapters on Spiritual Perfection. This is a concise and coherent manual of the monastic life. A polemical motif — the refutation of Messalianism — is very strong in this work. Diadochus helps us to understand the inner difficulties and dangers in the monastic life, in the life and "ordeal" of prayer, especially in chapters 76 to 80.