On the Incarnation

De incarnatione is the major christological treatise of Theodore of Mopsuestia, the Antiochene bishop and biblical commentator who died in 428. Written in Greek, it survives only in fragments, preserved mainly in Syriac and in Latin quotations and in the florilegia that later controversy produced. Its date is not known. Even so, it belongs to the setting that made Theodore a central figure of his age: the fourth-century struggle over how Christ can be fully God and fully human, the Arian and Apollinarian disputes that had pressed the question, and the Antiochene tradition's determination to defend the completeness of Christ's humanity against any teaching that diminished it.

Theodore's argument begins from the conviction that salvation requires a genuine human nature in Christ, with a real human soul, mind, and will. He rejects the Apollinarian view that the divine Word took the place of the human mind in Jesus, and he insists that the Word assumed a complete man, who grew, was tested, and learned obedience. To hold the two natures together, he speaks of the Word dwelling in the assumed man, and he explains the union through the language of indwelling, good pleasure, and the single prosopon, or person, in which both natures appear. The man Jesus is the shared face through which the Word acts and the humanity is honored. The treatise also carries Theodore's characteristic soteriology: Christ as the second Adam who overcomes where the first failed, leading humanity from mortality toward the stability of the age to come. His careful distinction between what belongs to each nature, and his reluctance to let divine attributes flow too freely into the human, is the heart of the work.

The treatise matters because it records, in Theodore's own words, one of the most influential and disputed ways of thinking about the incarnation. Theodore was condemned posthumously at the Second Council of Constantinople in 553, after Cyril of Alexandria's party and later critics associated his language with the position of Nestorius. His writings were nonetheless honored in the East Syrian Church, where he was called the Interpreter. Reading the surviving fragments is a way of testing the inherited caricature against what he actually wrote, and of seeing why the Antiochene concern for Christ's real humanity still presses on the church's confession.

Who should read this: students of patristic christology and of the road from Nicaea to Chalcedon, and readers who want to meet Theodore directly rather than through his opponents. It is not for those looking for a devotional or continuous narrative text, since the work survives only in fragments and assumes familiarity with the vocabulary of nature and person.