God’s Ad Extra Work of Incarnation

Every external work of the Godhead is indivisible, performed by Father, Son, and Holy Spirit. We have seen this in the work of creation, where the three persons all create the world (Gen. 1:1–3; Ps. 104:30; Eph. 3:9; Heb. 1:2). Each person does exactly the same work; They do not do it in the same way, however, but do it according to Their unique personal properties. The Father works from Himself because He is eternally unbegotten, the Son works from the Father because the Son is eternally begotten of the Father, and the Spirit works from the Father and the Son because He eternally proceeds from the Father and the Son. We thereby see each divine person working even though the work is one.

That brings us to appropriations, another important Trinitarian concept related to God’s ad extra—external—works. The concept of appropriations says that while every external work of God is the same work of Father, Son, and Holy Spirit, some works especially reveal a particular person. Thus, Scripture appropriates or attributes the sending of the Son to the Father. It does so not because the Father alone works the incarnation but because coming from God into the world illustrates in a special way the Son’s coming from the Father from all eternity. To understand this, let us ask, Who sent the Son into the world? The Father, of course, for that is what texts such as John 17:21 teach. That leads us to the next question: Did the Father alone send the Son into the world, or did the Holy Spirit and the Son participate in that sending as well?

The answer must be that it is a work common to all three persons of the Trinity. Galatians 4:4 indicates that the Son’s being sent into the world means that He was born of a woman, becoming incarnate. For that to happen, the human body and soul of Jesus had to be created, for the human nature of the Son did not exist from all eternity but came into being when the Holy Spirit overshadowed Mary (Luke 1:35). But because creation is the common ad extra work of the Trinity, Father, Son, and Holy Spirit worked the same work of fashioning the Son’s humanity. Augustine of Hippo writes that “because the will of the Father and the Son is one, and their working indivisible . . . , let [us] understand the incarnation and nativity of the Virgin, wherein the Son is understood as sent, to have been wrought by one and the same operation of the Father and of the Son indivisibly; the Holy Spirit certainly not being thence excluded.”