Putting our children to bed is always a precious time to read the Bible, sing hymns, and talk about the day. But precious as it is, it is not always simple.

A few days ago, as our five year old was minutes from dream land, he began asking questions about Jesus’ birth. I listened to my wife explain that Jesus had always existed. And I heard him respond, “Yes, but he was also born,” exposing the challenge that if Jesus was born than he must have had a beginning. Right?

Perhaps, we have the making of a little Arian in our home (as in Arius from the fourth century Africa, not the Third Reich in twentieth century), or perhaps he is simply experiencing the challenge that we all face when we begin to press into the incarnation of Jesus Christ. What does it mean that the eternal Son of God who was with God before the beginning of time (John 1:1) took on flesh and became a man in time?

The Incarnation

The subject of the incarnation is puzzling for adults let alone little boys with active imaginations. On this night, the difficulty came down to the debate between the Son’s eternal existence (in his divine nature) and the beginning of Jesus’ life on earth (in his human nature). I tried to explain as best I could, but I think he was asleep before we came to any ecumenical consensus.

How is it exactly that we are to understand and explain the co-eternal Son of God taking on flesh and becoming a human? In his humanity, the Son of God has a starting point, a beginning. But not in his deity. This point tripped up Arius (256-336 AD) and continues to puzzle Christians.

For those who want to seriously understand who Jesus is and what Jesus is (metaphysically speaking) we must introduce a few terms. These are concepts developed over the centuries have helped Christians speak about God without stepping into the heretical errors of Docetism, Apollinarism, and Nestorianism.

The three terms are (1) the hypostatic union (that’s union, not onion), (2) kenosis (not Kenosha, Wisconsin), and (3) the extra-Calvinisticum (or just the ‘extra’). Let’s look at each in turn.

Hypostatic Union

The hypostatic union is shorthand for the way in which Christ’s deity relates to his humanity and reverse. In the fourth and fifth centuries, debates raged about how Jesus could be God and man. Ultimately, the Chalcedonian Creed  in 451 AD, following and clarifying the Nicene Creed in 325 AD, made the confessional statement:

…Our Lord Jesus Christ, the same perfect in Godhead and also perfect in manhood; truly God and truly man, of a reasonable soul and body; consubstantial with the Father according to the Godhead, and consubstantial with us according to the Manhood; in all things like unto us, without sin; begotten before all ages of the Father according to the Godhead, and in these latter days, for us and for our salvation, born of the Virgin Mary, the Mother of God, according to the Manhood; one and the same Christ, Son, Lord, only begotten, to be acknowledged in two natures, [without confusion], unchangeably, indivisibly, inseparably; the distinction of natures being by no means taken away by the union, but rather the property of each nature being preserved, and concurring in one Person and one Subsistence, not parted or divided into two persons, but one and the same Son, and only begotten God (μονογενῆ Θεὸν), the Word, the Lord Jesus Christ; as the prophets from the beginning [have declared] concerning Him, and the Lord Jesus Christ Himself has taught us, and the Creed of the holy Fathers has handed down to us. (Cited in Philip Schaff, Creeds of Christendom, 30-31).

The language of ‘consubstantiality’ was used to describe the way that Jesus was both of one essence with the Godhead and of the same essence of humanity. And yet, when he took on flesh so that the fullness of God dwelt bodily (Col 1:19; 2;9), his two natures were now indivisible and inseparable but without confusion, mixture, or change. In one term, hypostatic union serves as the shorthand expression for all that was affirmed by Chalcedon.

Kenosis

Kenosis is a greek word that means ’emptied’ or ‘to empty.’ It comes from Philippians 2, where Paul writes that Christ “emptied himself” when he became a man. On the basis of this word and Charles Wesley’s hymn, many think that Christ really emptied himself “of all but love” or something else. On the basis of that term, they espouse that Christ left something of his deity in heaven. However, Scripture is more clear. In Philippians 2:6-7 reads,

though he was in the form of God, did not count equality with God a thing to be grasped, but emptied himself, by taking the form of a servant, being born in the likeness of men.

Notice Paul’s wording. Christ emptied himself “by taking the form of a servant.” To say it another way: Jesus emptied himself by addition, not subtraction.

Jesus, when he took on humanity, did not lose anything or leave anything behind. Rather, Christ in his deity added to his divine nature a human nature in which he lived out all of his days. Therefore, Christ now exists in two natures, not just one. In the Godhead, he alone is divine and human. The Father does not have a human nature. Neither does the Spirit. The alone is enfleshed and yet his humanity has not become part of the divine nature. As the first word encapsulates, he is a hypostatic union, which means that he exists in two ‘hypostases’ (essences) that are perfectly and indivisibly conjoined but not confused or combined.

The Extra-Calvinisticum

Last, to help bolster our understanding of Christ’s incarnation, we come to the Extra-Calvinisticum. This doctrine was espoused by Calvin, but it also predates Calvin. It teaches that the Son is not restricted to his earthly body. In other words, to quote the words of John Mayer, the Son really is “bigger than his body gives him credit for.”

Lutherans believe that the human nature is taken up into the Godhead, and in turn, they believe that Christ’s divine nature is circumscribed by his human body. (This explains why they believe that Christ is consubstantial with the elements at the Lord’s Supper). Against this view, Calvin and other Reformers argued that Christ’s deity extends beyond his human body. This is how he puts it in his commentary on John:

“It may seem absurd to say that he ‘is in heaven’ while he still lives on earth. If it is answered that this is true about his divine nature, then this expression would mean something else—namely, that while he was man he was ‘in heaven.’ I could point out that no place is mentioned here and that only Christ is distinguished from everybody else as far as his state is concerned, since he is the heir of the kingdom of God, from which the whole human race is banished. However, as very frequently happens, because of the unity of the person of Christ, what correctly applies to one of his natures is applied to another of his natures, and so we need seek no other solution. So Christ, who ‘is in heaven,’ has clothed himself in our flesh, so that by stretching out his brotherly hand to us he may raise us to heaven with himself.” (John Calvin, John, Crossway Classic Commentaries, 74-75).

And again in his Institutes:

“For even if the Word in his immeasurable essence united with the nature of man into one person, we do not imagine that he was confined therein. Here is something marvelous: the Son of God descended from heaven in such a way that, without leaving heaven, he willed to be borne in the virgin’s womb, to go about the earth, and to hang upon the cross; yet he continuously filled the world even as he had done from the beginning!” (John Calvin, Institutes of the Christian Religion, 1:481). (HT: Jared Wilson)

Put simply, when Christ took on flesh, his deity did not shrink to fit in his human body. Since he existed as one person in two natures, he both lived, moved, and had his being in the human body, but as the divine Son, he maintained his omnipresence, omniscience, and omnipotence—to name a few divine attributes.

Therefore, even as his human body died, the Word of God continued to uphold the universe. The reality of this ‘extra’ stretches our human understanding, but it preserves our awe of the Son who is God and not just man. In his humanity Christ is like us—fully human. But in his full personhood, he is nothing like us. He is our Creator and the one who has existed for eternity. Therefore, the Extra-Calvinisticum maintains his cosmic lordship, even as Christ in his human obedience won the right to rule heaven and earth as the Son of David.

Conclusion

Christology is a glorious thing, but it is immensely challenging. For those just starting to think more deeply on these matters, vocabulary is vital. Getting a handle on some of the theological concepts will help you better know the true Lord and worship our Triune God.

All in all, we must prayerfully embrace the concepts and truths described in these three words if we are going to be able to know who Christ is, what he is, and what he has done in taking on a human body and soul. Perhaps, they are not the words that my five year old is ready for, but I pray that one day that he and I might marvel at the God who emptied himself by taking on flesh and yet who still stands outside space and time to uphold the universe. These truths are glorious and worth much consideration. As Psalm 111:2 says, “Great are the works of the Lord, studied by all who delight in them.”

Soli Deo Gloria, dss