Nestorianism: the teachings of Nestorios, bishop of Contantinople (428-431), who explained the dual nature of Christ by supposing that he was fully human at birth, becoming divine during his ministry. Nestorios' interpretation affected the assessment of the nature of Virgin Mary, making her simply mother of Christ, rather than mother of God, which the third Ecumenical Council (Ephesus, 431) established as the orthodox position.