Nestorius, born in Euphratesian Syria 31 years after Theodore of Mopsuestia (c.381), was destined to have his name permanently linked with the great mepasqana because of his Dyophysite pronouncements and the adoption by the faculties of Edessa and Nisibis of his and Theodore's polemics and commentaries. Together, Theodore and Nestorius served as the wellsprings of the two Mesopotamian schools that carried the banner of Nestorianism.
Nestorius used his position as bishop of Constantinople (428) to preach against the title Theotokos, "Mother of God," that was given to the Virgin Mary. He claimed a more authentic title should be the Mother of Christ. This doctrine was challenged by Cyril of Alexandria and, later, Pope Celestine, who anathematized Nestorius and condemned him as a heretic at the Council of Ephesus in 431.
Although much of Nestorius's sermons and teachings were ordered to be burned, the doctrine of Nestorianism survived and served as the basis for Dyophysite teachings in the fifth and sixth centuries, particularly at Nisibis, which had inherited the mantle of Syrian scholarship from Edessa. Fragments of Nestorius's letters and sermons have been preserved in the Acts of the Council of Ephesus, citations in the works of St. Cyril of Alexandria (Nestorius's creedal adversary), and through the interpolated Syriac text, The Bazaar of Heracleides, an apology, written near the end of his life (c. 436).
The Christological thought of Nestorius is dominated by Cappadocian theology and is influenced by Stoic philosophy. Although Nestorius never spoke of the human Jesus and the divine Jesus as "two sons," he did not consider him simply as a man. However, differing from Cyril of Alexandria, who posited one sole nature (mia physis) in Christ, Nestorius defined a nature in the sense of ousia, "substance," and distinguished precisely between the human nature and the divine nature, applying in his Christology the distinction between nature (ousia) and person (hypostasis). Nestorius refused to attribute to the divine nature the human acts and sufferings of Jesus. This last statement underlines the ultimate difference between Nestorius and Cyril. Nestorius distinguished between the logos (the "divine nature") and Christ (the Son, the Lord), which he saw as a result of the union of the divine nature and the human nature. After the Council of Ephesus, a strong Nestorian party developed in eastern Syria that found its strength and intellectual support in the School of Edessa. After the theological peace achieved in the agreement of 433 between Cyril of Alexandria and John of Antioch, a number of dissenting bishops affiliated themselves with the Syrian Church of Persia, which officially adopted Nestorianism at the Synod of Seleucia in 486. The Nestorians were expelled from Edessa in 489 by the Emperor Zeno and emigrated to Persia. It was thus that the Nestorian Church broke away from the faith of the Church of Constantinople and the Byzantine Empire.
The Nestorian spirit was redoubtable. Secured in the Persian Church, it continued to flourish in the seventh century despite persecution from the Sassanids, and after the invasions of the Turks and Mongols. Nowhere is its intellectual vibrancy and spirit more apparent than in its theological school, Nisibis, the successor to Edessa. It is here where our narrative leads, and the explication of the environment that produced Paul's Dyophysite text and Junillus's Instituta Regularia Divinae Legis begins.