Brief Life and Teachings
Saint Diadochos was born around 400, and served as the Bishop of Photiki in Epirus of Northern Greece. In 451, he took part in the Fourth Ecumenical Synod of Chalcedon as Bishop of Photiki, and supported Orthodoxy against the Monophysites. He was most likely part of a group of notables from Epirus who were captured during a Vandal raid between 467 and 474. The group was later released in North Africa, somewhere around Carthage, from whence all vanished. His exact date and place of death are thus unknown, although it is assumed he died before 486.
Diadochos' writing and ascetic practice were greatly influenced by Evagrius the Solitary (also known as Evagrius Ponticus) and Saint Makarios of Egypt (the Great), incorporating their ideas of hesychia (Greek ησυχία, "stillness, rest, quiet"), sensible spiritual experience, and the fierceness of the fight against the demons. People begin their lives in innocence, a state out of which they naturally grow; leading a life of virtue and prayer through the praxis of ascetcism creates a state of informed innocence, the state summed up in Christ's injunction to be as wise as serpents and as harmless as doves. The resulting love and theoria are the wellspring of Christian doctrine. Great importance is paid to the continual remembrance and invocation of the name of Jesus.
His best-known work, On Spiritual Knowledge and Discrimination (known as the "One Hundred Chapters"), was written for his monks in reaction to strange doctrines coming from the heretical Messalian sect in Mesopotamia (also known as Euchites), who taught that each person has a personal demon to be exorcized by constant prayer. He is also thought to be the author of a sermon on the Ascension and a dialogue with St. John the Baptist.
Although Diadochos is not officially recognized as a saint of the Church in the synaxaria, he is honored in some old manuscripts as one and is commonly celebrated today on March 29th.
Introduction of St. Nikodemos the Hagiorite to the "One Hundred Chapters" of St. Diadochos of Photike in the Philokalia
Our Holy Father Diadochos, who served as Bishop of Photiki in Old Epirus of Illyria, lived before the seventh century, which we infer from the writings of Saint Maximus the Confessor, who refers to the Chapters of Diadochos.
Anyone who wants can see that he was resplendent in praxis and theoria by comprehending this work, which he excellently composed after philosophical trials of many years, and having experienced divine ascents in his heart. Having divided it into 100 chapters and having revealed with all precision the deepest secrets of the operations of prayer, and having filled it densely with words from Holy Scripture and precise spiritual knowledge through theoria, as an example of the teachings of the work of the sacred neptics consisting of all the virtues, he left it for just about all the neptic and God-bearing fathers after him.
Because of this, you can also find many of them in frequent admiration of these chapters in their neptic works, as if finely worked paintings, and pull from them help and confirmation. The sacred Photios also makes mention of these chapters in text 201 with these words: “These 10 Definitions are followed by the 100 Chapters, and this is an excellently conceived work for those who practice asceticism towards virtue, and for those who exercise in the work that brings one to perfection, not saying anything unclear.” Moreover, the Synod which met in the presence of Andronikos Palaiologos, Gregory of Thessaloniki, Symeon of Thessaloniki, Gregory of Sinai, and the most holy Kallistos, and many others, attest that the work is blameless.
And if the century of chapters of which Photios speaks appears to contain something wrong, just the same the divine Maximus banishes from us all doubts, interpreting its meanings according to the correct view of piety, as you see at the end of these chapters.