. The doctrine first set forth officially in the definition produced by the Council of Chalcedon (451), concerning the union of the two natures (dyo physeis) of deity and humanity in the one hypostasis or person of Jesus Christ. In the incarnation of the Son of God, a human nature was inseparably united forever with the divine nature, yet with the two natures remaining distinct, whole, and unchanged, without mixture or confusion, so that the one person, Jesus Christ, is truly God