Nestorian Schism

The Nestorian Schism (431–544), in church history, involved a split between the Christian churches of Sassanid Persia, which affiliated with Nestorius, and churches that rejected him. The schism rose out of a Christological dispute, notably involving Cyril (Patriarch of Alexandria) and Nestorius (Patriarch of Constantinople). The First Council of Ephesus in 431 and the Council of Chalcedon in 451 condemned Nestorius and his doctrine, which emphasized the distinctness between Christ's human and divine natures.

That forced a breach between the churches that defended Nestorius and the state church of the Roman Empire, which caused the Church of the East, the Christian church of Sassanid Persia, to become known as the Nestorian Church, as it took the side of Nestorius.

Despite ratifying the Council of Chalcedon at the 544 Synod of Mar Aba I, the Christians of the Church of the East have ever since been most commonly but inaccurately known as the Nestorians.

The doctrine of Nestorianism is associated with Nestorius, the Patriarch of Constantinople from 428 to 431. Prior to becoming Patriarch, Nestorius had been a student of Theodore of Mopsuestia at the School of Antioch. Nestorius argued that Christ's human and divine natures were distinct and so he was against using the title Theotokos (Greek: "God bearer") for the Virgin Mary. He preferred to call her Christotokos ("Christ bearer"). Cyril of Alexandria considered the doctrine contrary to Orthodox teaching and encouraged measures against it.

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