Marcus Diadochus (Markos ho diadochos) was a Christian writer of the fourth century. Nothing is known of him but his name at the head of a "Sermon against the Arians", discovered by Wetsten in a manuscript codex of St. Athanasius at Basle and published by him at the end of his edition of Origen[1] Another version of the same work was lent by Galliciollus to Galland and published in the "Veterum Patrum Bibliotheca", V (Venice, 1765-1781). This is the text in Patrologia Graeca[2] The sermon quotes and expounds the usual texts[3], and answers difficulties[4].
A quite different person is Diadochus, Bishop of Photike in Epirus in the fifth century, author of a "Sermon on the Ascension" and of a hundred "Chapters on Spiritual Perfection" [5], whom Victor Vitensis praises in the prologue of his history of the Vandal persecution[6]. The two are often confounded, as Migne does.
This article incorporates text from a publication now in the public domain: Herbermann, Charles, ed (1913). Catholic Encyclopedia. Robert Appleton Company.