مجمع خلقيدونية
In 451, the Ecumenical Council of Chalcedon promulgated the Chalcedonian Definition. It agreed with Theodore that there were two natures in the Incarnation. However, the Council of Chalcedon also insisted that hypostasis be used as it was in the Trinitarian definition: to indicate the person (prosopon) and not the nature as with Apollinaris.