Before I married my wife three decades ago, I was an unrepentant pack-a-day smoker. I was in my final year of seminary and on a regular basis, would participate in what I called the Lardman Triathlon. I’d take the elevator down from my third-floor dorm room, hop in my standard-transmission Plymouth Reliant, and drive the block and a half to the Speedy Market to buy a six-pack of Mountain Dew and a pack of Merit Ultra Light Menthols. I miss my days of being a chimney, not just for the ability to use my 6” x 6” glass ashtray in the faux leopard skin box, but for the ability to use one of those smokes to teach about the hypostatic union of Christ.

That’s a fancy theological phrase. It first appeared in English in 1678 in Ralph Cudworth’s work, “True Intellectual System of the Universe: The First Part; Wherein, All the Reason and Philosophy of Atheism Is Confuted; and Its Impossibility Demonstrated.” Whew. But there’s more. Here’s what he said: “The Humane Soul of our Saviour Christ himself…being not Partially appointed to that transcendent Dignity, of its Hypostatick Union, but because of its most faithful adherence to the Divine Word and Wisdom, in a Pre-existent State.” I’m not sure a sentence full of 17th-century verbiage would convince convicted atheists to part company with their godless ways. But understanding the doctrine of the hypostatic union can help us understand what God is up to in the Incarnation.

In my actively addicted life, two things were important to gain nicotine’s benefit of both the rush and calm of staving off withdrawal: the tobacco and the paper. One without the other was useless and couldn’t deliver the benefits I sought. Both were needed to keep the stick smoldering so that I could be infused with all my Ultra Lights had to offer. In the same way, the hypostatic union of Christ – Jesus’ identity as both fully human and fully divine – are required for bestowing his benefits to sinners like me. These two things work in tandem to make the delivery system the Spirit uses to bring the gifts of the Son of God.

Understanding the doctrine of the hypostatic union can help us understand what God is up to in the Incarnation.

In his Ökumenische Dogmatik (Ecumenical Dogmatics), the 20th-century German theologian Edmund Schlink (1903-1984) pointed to the language of the Apostles’ Creed as the center of our thinking about the hypostatic union of Christ. In the Creed, we confess that God’s Son was “conceived by the Holy Spirit and born of the virgin Mary.” The conception by the Spirit is God’s decision to disclose his very self, a divine expression like a nursing mother expressing milk for the sake of her child. The Spirit’s conception is God’s action that shows Jesus’ divine nature. He exists as God’s very presence in this world. Schlink said,

He, through whom God sustains the universe, has entered into the context of creatures, who, in their own action and development, depend on God to sustain them. He has come under the destiny given to all creatures, both living and dead, to glorify God as part of the creation along with every other creature [My translation].

The ancient heresy of Adoptionism argued that Jesus was human but not divine and that God simply adopted him when he was baptized by John. But the Scriptures counter with a babe laid in the Bethlehem manger who is God indeed. God’s own attributes are present in him, and he bears the certain mark of Jeremiah’s promised new covenant. Christ comes slow in anger and abounding in steadfast love: “They shall all know me, from the least of them to the greatest, says the Lord; for I will forgive their iniquity, and remember their sin no more” (Jer 31:34b). Jesus’ miracles, casting out of demons, and ability to command the winds and the waves all attest to divine power. But it’s in his death and resurrection that we see the depths of his love and mercy fully. And it’s this good news where we truly come to know God because that’s where we discover God’s long-term memory problems. On account of the divine Son of God, we see how the Lord deals with our sin and brokenness. “Sin? What sin?” he says. “Didn’t Jesus handle that for you?”

The other side of the hypostatic coin is Christ’s humanity. In Philippians 2:6, Paul reminds us that, though Christ “was in the form of God, [he] did not regard equality with God as something to be exploited, but emptied himself, taking the form of a slave.” God’s godliness is so alien and inaccessible to us that in the Jerusalem temple, he remained hidden behind the curtains in the Holy of Holies. Yet at Jesus’ final breath on the cross, the curtain was rent top to bottom. (That’s thirty feet of shredded, spendy velvet.) The utter ignominy of the Divine One dying an entirely human death became the moment that he is fully one with us. And it’s not that with a ripped curtain we can now enter into the sanctum sanctorum. It’s that, having emptied himself to the point of our most common experience and loss, he refuses to be cooped up in a holy box.

Other ancient heresies like Gnosticism and Docetism forced the church to be explicit about Jesus becoming fully human. Gnosticism sneered at the material world and couldn’t imagine a divine being would stoop to having a physical body. Docetism said that Jesus’ humanity was merely an illusion. Those heresies asserted in their own fashions that Jesus only appeared to be human. In their distaste for a God who dies as a human being, some traditions went so far as to argue that it wasn’t the divine Jesus crucified on the cross but that someone else – usually Simon of Cyrene – slipped in on the way to Golgotha and was crucified instead.

From first breath to last, he was human.

But Jesus breathed his first breath in a barn, had his messy swaddling clothes changed, ate pomegranates, got blisters from his sandals, hit his thumbs with Joseph’s hammers, experienced being forsaken by God, and expelled a final lung-full of air. From first breath to last, he was human. God so loved the world that he was willing to muck about in the mire of human existence.

Sinless guy that he was, Jesus didn’t need to be baptized by John in the Jordan. But what was in that water was the flotsam and jetsam of the sins of the people of Jerusalem and the surrounding countryside who’d come out to be washed by Jesus’ baptizing cousin. When I was a kid, my parents didn’t want to waste water, and whatever electricity was needed for a hot bath, so they had us three kids take consecutive baths. By the time the last of us climbed out, there was a nasty ring of soap scum and Jones kids’ skin cells around our mid-century modern bathtub. Add sin to the mix, and you’ve got Jesus being baptized into our very human sin.

In place of the common assumption religion has of the Christian life as something we practice, as an activity in which we strive to become more and more godly (as if we’ve ever had any success climbing Jacob’s ladder), the hypostatic union of Christ turns things upside-down. The direction God chooses is to become human while still retaining his own divine job description: “I will have mercy on whom I will have mercy. And I’ll die to get it done.” (Rom 9:15ish).

In Jesus Christ, conceived by the Holy Spirit and born of the Virgin Mary, the volatile mix of human and divine becomes an explosive rendering of compassion. It’s like potassium and water. Bam! Mercy! Nothing dry and boring here.