A member of the Antiochene school of theology, Nestorius began his work from the Synoptic Gospels and tried to explain how the man presented there is also God (pg. 144). As an Antiochene, he also began from diversity and tried to work his way to unity. He rejected the by-then traditional term for Mary, “Theotokos” (God-Bearer), for two major reasons. First, he felt it could be construed in an Arian fashion, as if implying that the Son was a creature born of a creature. Second, he felt it could be construed in an Apollinarian fashion, as if the Word “completed” the mere human person Jesus (pg. 145).
To avoid these seeming implications of “Theotokos,” Nestorius held that Mary was “Christotokos,” the “Christ-Bearer,” where “Christ” was both God and Man. For Nestorius, Christ had two natures–two distinctly individual expressions of objective being (prosopon, or hypostasis). But neither of these natures was an actually subsistent entity; each instead “remained unaltered and distinct in the union, the Godhead existing in the man; the man , in the Godhead without mixture or confusion” (Davis, pg. 146). He cites Nestorius: “Christ is indivisible in His being Christ, but He is twofold in His being God and man. We know not two Christs or two Sons or Only-Begottens or Lords, not one and another Son, not a first and a second Christ, but one and the same, who is perceived in His created and His incarnate natures” (ibid.).
Nestorius preferred the term “conjunction” rather than “union” for the relationship between the two natures, because he deeply desired to preserve the truth that the natures were not confused or mixed. The conjunction, moreover, came about by the cooperative gracious condescension of God and the loving obedience of the man, and it resulted in a single prosopon, Christ, “that is, one object of perception, one external undivided appearance” (Davis, pg. 146). Because the two natures remain distinct and “neither is identical with the prosopon of union,” all human attributes belong to the human nature and all divine attributes to the divine. But, the conjunction of two natures means that all the attributes, human and divine, belong to the one prosopon, Christ. Now since it is the one prosopon Christ who was born of the Virgin Mary, she should be called Christotokos, the Christ-Bearer (pg. 147).
Davis charitably calls this theory “a laudable attempt to preserve intact and complete the two natures, Godhead and manhood, of Christ.” Nevertheless, Nestorius’ problem was that he failed to achieve his Antiochene goal of moving from diversity to unity. His unifying conjunction, the one prosopon Christ, “could not adequately explain to the satisfaction of the Church the union of the two complete and objectively real natures which he sought so sincerely” (ibid.). Citing G.L. Prestige’s judgment, Davis observes that Nestorius’ heresy was not “a positive fact but a negative impotence” (ibid.).