One Person, Two Natures
The fifth century church condemned two heresies concerning the definition of Jesus Christ: (1) Monophysites taught that Christ had only one nature, either all human, or all divine, or a mixture of divine and human; (2) Nestorians said if Christ has two natures, one divine and the other human, then He must be two separate persons.
The Chalcedonian Council (451)
The Council of Chalcedon declared that Christ is one person with two natures – truly man and truly God – perfectly united in one person, with no mixture, confusion, separation, or division. The words “no mixture or confusion” (directed at Monophysites) mean the divine and human natures are not blended to make a deified human nature or a humanized divine nature. The human nature is always human, and the divine nature is always divine, ‘each nature retaining its own attributes.’ The words “no separation or division” (directed at Nestorians) affirmed that the two natures are different but not separated or divided from each other so as to make two persons (just like light and heat are different but not separated).
When the Son of God became a Man, He did not lay aside any of His divine attributes. The divine nature of Christ is eternal, immutable, omniscient, and omnipotent. His human nature is finite and restricted by space and time.
Jesus acted according to both His humanity and His divinity. When He perspired in the garden of Gethsemane, it was not His divine nature that sweated. God does not sweat. Likewise, God does not get hungry, bleed, or cry. It was the human nature, not the divine nature that died on the cross. God’s divine nature cannot die.
When Jesus said He did not know the timing of His own return (Mark 13:32), it obviously was a statement of His humanity. Christ knew everything according to His divine mind, but He did not know everything according to His human mind. When Christ revealed things that no human could possibly know that was a case of the divine nature communicating knowledge to the human nature.
No one has ever penetrated the depths of how Christ can be truly God and truly man. We have one who is sui generis. He is in a class by Himself. Only one person in all human history has ever been God incarnate, and the mystery of the incarnation is beyond our full understanding.
[Adapted from Everyone’s a Theologian by R.C. Sproul]