Theodorus of Cyzicus (Θεόδωρος ὁ Κυζικηνός)

Life Theodorus of Cyzicus was a late antique author of the 5th–6th century CE, known only from his ethnonym, which identifies him as originating from Cyzicus in the province of Hellespontus [1]. No biographical details of his life or education survive.

Works His sole extant work is the Epistle to the Alexandrians (Ἐπιστολὴ πρὸς Ἀλεξανδρεῖς), preserved in the acts of the Second Council of Nicaea (787 CE) [1]. This Christological letter defends the doctrine that Christ assumed a complete human nature, including a rational soul, arguing against the 4th-century teachings of Apollinarius of Laodicea [1].

Significance Theodorus’s significance stems from the later use of his letter at the Second Council of Nicaea. The council fathers cited it as a patristic authority against the Iconoclasts, interpreting its defense of Christ’s full humanity as theological justification for the depiction of Christ in icons [1]. Thus, his anti-Apollinarian text was repurposed for the 8th-century iconoclastic controversy.

Sources 1. Perseus Digital Library (Tufts University): http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A2008.01.0620%3Achapter%3D13