Introduction
“Come behold the wondrous mystery, Christ the Lord upon the Tree. In the stead of ruined sinners hangs the Lamb in Victory!” Matt Boswell uses such wonderful language to point to the profound mystery of Christ being both God and Man and the one Savior for sinners.
As we saw previously, Jesus is not merely a man but is both true God and true Man united in one Person. Understanding this truth is crucial for grasping the depth and sufficiency of his life, death, and resurrection.
A Man Like Us Yet Without Sin
The foundational truth of Jesus' humanity is all over the Gospels. He was conceived in the womb of the virgin Mary (Mt. 1:18-25). He experienced the full range of human existence (Heb. 4:15). He was born of His mother in this world in a particular time and day (Gal. 4:1-7). Yet, He is also the eternal begotten Son from the Father.
Early church fathers like Cyril of Alexandria emphasized this Hypostatic Union, clarifying that God did not simply join Himself to a pre-existing man—a human person. Cyril says the Son of God Himself came in that form fully embracing human nature while remaining in His divine likeness to the Father.
The Gospels paint a vivid picture of Jesus' human life: He grew, ate, drank, slept, cried, and touched. He experienced the full range of human emotions. He had legs to walk with and hands to grab objects with. Even in His most agonizing moment on the cross, as Cyril notes, Jesus could cry out, "'My God, My God, why have you forsaken me?' as one of us and on behalf of all human nature." This most intimate identification with humanity underscores the genuineness of his human experience. There is no Christ if there was no full assumption of human nature. As Girolamo Zanchi says, "Whenever we read that He did or suffered something on our behalf according to His human nature, we believe He truly and really did and suffered all those things."
But, we must hold onto the following: This truth does not imply any separation from or confusion with his divine nature. There was not a dissolution of the Holy Trinity on the Cross.
The GodMan
The suffering and death of Jesus on the Cross are central to Christian theology. There is no Christianity without it. If Jesus were only divine and incapable of suffering, His crucifixion would be a facade which was devoid of authentic human pain and suffering. He must be Man. He must have a human nature. Yet, He must also be God.
The problem is: How can an impassible God suffer for our sins?
Some want to make God passible and capable of suffering. This would be a big problem as Thomas Weinandy points out, "If the Son of God experienced suffering in His divine nature, then it would be God suffering as God in a man.” Which means that the Cross would not constitute genuine human suffering and, therefore, not a suffering on our behalf.
Because Jesus is both "true God" and "true man" without any confusion of these natures, He could truly experience and know our suffering in his human nature. This Hypostatic Union—one Person with two natures—is the very foundation of His ability to be the Mediator between God and Man.
Philippians 2:6-8 beautifully describes this reality: "Though he was in the form of God, He 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. And being found in human form, he humbled himself by becoming obedient to the point of death, even death on a cross." This "emptying" was not a cessation of His divinity but a willing veiling of its full glory in order to truly embrace humanity. Zanchi further clarifies this by stating that "the Son of God was not made man by confusing His divine nature with the human in any way...but only by assuming a human nature into the unity of His person."
The Coolest Name For A Doctrine: Communicatio Idiomatum
The divine nature and the human nature, each retaining their distinct properties, are perfectly and indivisibly united in the one Person of the Son of God. Cyril of Alexandria says, "Godhead is one thing, and manhood is another thing, considered in themselves, but in the case of Christ they came together in a mysterious and incomprehensible union without confusion or change. The manner of this union is entirely beyond conception." He offers an analogy: just as a human being has a single nature comprised of both body and soul, so too Jesus is one Person with two natures.
This union meant that the human nature of Jesus became the true temple and the true Holy of Holies, the very dwelling place of God in a way even the Old Testament temple could not fully encompass (Jn. 1:14). This means that Jesus' saving acts were not performed by His human nature alone. If that were the case, His sacrifice would not possess the infinite worth sufficient to atone for all the sins of all the elect and reconcile us to God.
We must also guard against the thought over-separating the two natures of Christ that result in two Persons or two Christs. There is not one Person who is "Jesus the Man" and another person who is "Jesus the God". There is one Person, the Son of God, who is both true God and true Man.
Here comes that amazing term for a vital doctrine: Communicatio Idiomatum, or the communication of properties. This doctrine is what we use to speak divine things about Christ and human things about Christ yet not saying His human nature is divine nor that His divine nature is human. He, the one Person, is both divine and human.
This protects us from saying that the divine nature suffered or that the human nature became infinite. The one Person of the Son of God is mysteriously both infinite and finite, impassible in His divinity yet truly suffered in his humanity. Acts 20:28 speaks this way when it says, "church of God, which He obtained with his own blood.”
“But, God doesn’t have blood!” Yes, we know! But, as Christ is both God and Man, we can embrace the mystery of attributing the act of shedding blood (a human act) to Christ who is also the eternal Son of God because of the inseparable union of the divine and human in Christ's Person.
Is this not amazing?!?
Listen to John Flavel as he says, "The human nature [was] doing what is human: Suffering, sweating, bleeding, dying. And the Divine Nature doing what is divine: Stamping all this with infinite value." Nehemiah Coxe echoed this, stating, "The Person that died was very God...but it was in the human nature and not in His divine nature that He suffered, although both made one Person."
One Person, Two Natures = One Savior
The necessity of the Incarnation—God becoming truly human—is further highlighted by considering the implications if God could suffer in his divine nature. As Samuel Renihan states, "If God can sustain suffering in His divine nature, why was the incarnation necessary?"
The Incarnation was the unique and singular act by which the Son of God, while remaining truly divine (transcendent and impassible in his divine nature), entered into human existence (becoming immanent and capable of suffering in his human nature). Consider the burning bush that contained fire and wood in perfect union without the wood being consumed. It’s not a perfect analogy but it’s similar to how the Son of God was truly present in our flesh on the Cross, His divine nature unchanged and unsuffering, yet His very Person experiencing the depths of human pain.
While the precise nature of this union remains a mystery—and we need to be OK with that—we must be careful not to confuse the language used to describe Christ. The divine nature did not change or suffer in any way due to the Incarnation. At the same time, to deny the fullness of Jesus' humanity would have devastating consequences. If He were not true Man, then His resurrection would be a deception. His atonement would lack genuine human sacrifice. Its worth would be insufficient to save a multitude. The truth that Jesus is true Man, united inseparably with His true divinity, is the bedrock of Christian hope and salvation.