That Christ Is One

That Christ Is One is one of St Cyril of Alexandria’s clearest explanations of the Church’s confession that Jesus Christ is one Lord and Son. In dialogue form, Cyril insists that the eternal Word truly became man without ceasing to be God and that His humanity is neither a separate human subject nor dissolved into the divinity. This unity shapes the whole saving mystery: the one born of the Virgin Mary, who suffers and rises in the flesh, is the same divine Son, and His own flesh is life-giving because it belongs to the Word Himself.

Modern scholarship generally places the dialogue in Cyril’s mature post-Ephesus period, around 438 or later, several years after the Council of Ephesus in 431. The council had condemned Nestorius, but debate continued over how Christians should speak of the distinction and unity of Christ’s divinity and humanity. Cyril argues against accounts that, in his judgment, left the Word and the man Jesus joined only by an external conjunction, while he also rejects confusion or change in the Incarnation. The work belongs to the final phase of his Christological controversy and presents his teaching in a settled, explanatory form.

The dialogue proceeds by question and answer through the biblical language Christians use about Christ. Cyril begins with the Son’s true divinity and the Word’s becoming flesh, then explains the title Christ, the self-emptying of Philippians 2, and the difference between true union and a merely external conjunction. He answers objections drawn from Christ’s growth, obedience, prayer, fear, suffering, and death, insisting that these genuinely human experiences belong to the one Son in His flesh. The closing argument turns to resurrection, salvation, and Christ’s life-giving flesh and blood, which Cyril insists are the Word’s own and not those of another human subject.