late 5th – 8th centuries

Three Eastern parties: Nestorians, Jacobites and Chalcedonians (Leontius, John of Damascus)

Pelikan regards the 7th–9th centuries as decisive, when the Nestorians, the Monophysites (Jacobites) and the Chalcedonians stated their positions so sharply that the division became final. The defenders of Antiochene christology formed a "Nestorian" communion in Persia: the school of Nisibis and Narsai ("two natures, two hypostases and one appearance"), the synod of Seleucia in 486, and at the beginning of the 7th century Babai the Great with the formula "two natures, two hypostases, one person of sonship". The Jacobites, relying on Cyril and Severus, taught that the one incarnate God the Word is the subject of all actions, and defended the addition "who was crucified for us" to the Trisagion. The Chalcedonians answered by distinguishing nature (the common) and hypostasis (the particular): Christ has one composite hypostasis and two natures; Leontius of Byzantium and John of Damascus taught that the human nature of Christ is not impersonal but "enhypostatic" – it exists in the hypostasis of the Word.