The meaning of hypostatic union is much easier than the term sounds, but the concept is as profound as anything in theology.
Our English adjective hypostatic comes from the Greek word hupostasis. The word only appears four times in the New Testament — maybe most memorably in Hebrews 1:3, where Jesus is said to be “the radiance of the glory of God and the exact imprint of his nature.” Here the author of Hebrews uses the word in reference to the oneness of God. Both the Father and the Son are of the same “nature.” Jesus is “the exact imprint of his nature.”
However, in early church discussions, as Greek thinkers tried to find agreeable terms with those who spoke in Latin, the word hupostasis came to denote not the sameness in the Godhead (God’s one essence) but the distinctness (the three persons). So, it began to be used to refer to something like the English word person.
Personal Union of Two Natures
“Hypostatic union” sounds fancy in English, but it’s actually a simple term. Hypostatic means personal. The hypostatic union is the personal union of Jesus’s two natures.
“The hypostatic union is the mysterious joining of the divine and the human in the one person of Jesus.”
Jesus has two complete natures: one fully human and one fully divine. What the doctrine of the hypostatic union teaches is that these two natures are united in one person in the God-man. Jesus is not two persons. He is one person. The hypostatic union is the joining (mysterious though it be) of the divine and the human in the one person of Jesus.
What Is the Significance?
Why bother with this fancy term? What importance is there in knowing about this hypostatic union? At the end of the day, the term itself it not essential, but the concept behind the term is infinitely precious — and worshipfully mind-stretching.
It is immeasurably sweet, and awe-inspiring, to know that Jesus’s two natures are perfectly united in his one person. Jesus is not divided. He is not two people. He is one person. As the Chalcedonian Creed states, his two natures are without confusion, without change, without division, and without separation. Jesus is one.
This means Jesus is one focal point for our worship. And as Jonathan Edwards preached, in this one-person God-man we find “an admirable conjunction of diverse excellencies.”
Because of this hypostatic (one-person) union, Jesus Christ exhibits an unparalleled magnificence. No one person satisfies the complex longings of the human heart like the God-man.
God has made the human heart in such a way that it will never be eternally content with that which is only human. Finitude can’t slake our thirst for the infinite.
And yet, in our finite humanity, we are significantly helped by a point of correspondence with the divine. God was glorious long before he became man in Jesus. But we are human beings, and un-incarnate deity doesn’t connect with us in the same way as the God who became human. The conception of a god who never became man (like Allah) will not satisfy the human soul like the God who did.
One Person — for Us
“No one person satisfies the complex longings of the human heart like the God-man, Jesus.”
And beyond just gazing from afar at the spectacular person of Jesus, we also have the amazing gospel-laced revelation that the reason Jesus became the God-man was for us. The personal union of God and man in him is personal for us. His fully human nature joined to his eternally divine nature is permanent proof that Jesus, in perfect harmony with his Father, is unstoppably for us.
He has demonstrated his love for us in that while we were still sinners, he took our nature to his one person and died for us (Romans 5:8).