J. I. Packer on the Incarnation

'Trinity and Incarnation belong together. The doctrine of the Trinity declares that the man Jesus is truly divine; that of the Incarnation declares that the divine Jesus is truly human. Together they proclaim the full reality of the Savior whom the New Testament sets forth, the Son who came from the Father’s side at the Father’s will to become the sinner’s substitute on the cross (Matt. 20:28; 26:36-46; John 1:29; 3:13-17; Rom. 5:8; 8:32; 2 Cor. 5:19-21; 8:9; Phil. 2:5-8).
The moment of truth regarding the doctrine of the Trinity came at the Council of Nicaea (A.D.325), when the church countered the Arian idea that Jesus was God’s first and noblest creature by affirming that he was of the same “substance” or “essence” (i.e., the same existing entity) as the Father. Thus there is one God, not two; the distinction between Father and Son is within the divine unity, and the Son is God in the same sense as the Father is. In saying that Son and Father are “of one substance,” and that the Son is “begotten” (echoing “only-begotten,” John 1:14, 18; 3:16, 18, and NIV text notes) but “not made,” the Nicene Creed unequivocally recognized the deity of the man from Galilee.

A crucial event for the church’s confession of the doctrine of the Incarnation came at the Council of Chalcedon (A.D.451), when the church countered both the Nestorian idea that Jesus was two personalities—the Son of God and a man—under one skin, and the Eutychian idea that Jesus’ divinity had swallowed up his humanity. Rejecting both, the council affirmed that Jesus is one divine-human person in two natures (i.e., with two sets of capacities for experience, expression, reaction, and action); and that the two natures are united in his personal being without mixture, confusion, separation, or division; and that each nature retained its own attributes. In other words, all the qualities and powers that are in us, as well as all the qualities and powers that are in God, were, are, and ever will be really and distinguishably present in the one person of the man from Galilee. Thus the Chalcedonian formula affirms the full humanity of the Lord from heaven in categorical terms.'

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