Nestorianism

Nestorianism is a Christian theological doctrine that upholds several distinctive teachings in the fields of Christology and Mariology. It opposes the concept of hypostatic union and emphasizes that the two natures (human and divine) of Jesus Christ were joined by will rather than personhood. This Christological position is defined as radical dyophysitism. Nestorianism was named after Christian theologian Nestorius (386–450), Patriarch of Constantinople 428-431, who was influenced by Christological teachings of Theodore of Mopsuestia at the School of Antioch.

Nestorius' teachings brought him into conflict with other prominent church leaders, most notably Cyril of Alexandria, who criticized especially his rejection of the title Theotokos ("God-bearer") for Mary, Mother of Jesus, and issued 12 anathemas against him at a council in Rome in 430. Nestorius and his teachings were eventually condemned as heretical at the Council of Ephesus in 431, and again at the Council of Chalcedon in 451, which led to the Nestorian Schism; churches supporting Nestorian teachings broke with the rest of the Christian Church.

Following that, many of Nestorius's supporters relocated to the Sasanian Empire, where they affiliated with the local Christian community, known as the Church of the East. However, some such as Sebastian Brock consider referring to the Assyrian Church of the East as the "Nestorian Church" to be "inappropriate and misleading."

Nestorianism in Agent of Byzantium

During the Ecumenical Council of 1317, on the issue of Iconoclasm, Arsakios the patriarch of Alexandria raised a clever paradox in opposition to Icons. If an Icon depicts only Jesus Christ's human nature, then it falls into the Nestorian heresy. If it depicts Christ's divine nature then it denies His human nature and so falls into the Monophysite heresy. In either case, Icons becom a snare of Satan and should be banned.