Jesus Christ is both fully God and fully man, and yet is one person. In this essay, I will defend the dual nature of Christ’s humanity and deity. Then, I will explain why this reality is crucial for the salvation of the world.
The duality of Christ begins in Mary’s womb. The Bible states: “that which is conceived in Mary is of the Holy Spirit (Matt. 1:20). This demonstrates that God actually took on human flesh by being born into the world, but he was free from sin since he had no father. He was overshadowed by the Holy Spirit, which prevented him from original sin. For the Scripture states: “God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons (Gal. 4:4-5).”
There are several scripture references that indicate Jesus was fully human. Let’s look at a few of these. Luke 2:40-52 says that Jesus grew up and increased in wisdom. He was tired on his journey to Samaria (Jn. 4:6), he became thirsty (Jn. 19:28), hungry (Matt. 4:2) experienced emotions (Matt. 26:38), and was perceived by others as a physical being like them during his three year ministry. These limitations reveal that Jesus had a real physical body and mind similar to that of other humans.
It’s also clear from the Bible that Jesus was fully God. Paul wrote in Colossians 2:9 that the fullness of deity dwells in Christ. When Jesus stilled the storm, it showed his power over nature (Matt. 8:26-27). He also did many miracles like multiplying the loaves and fish, changing water into wine, and rising from the dead. When Jesus saw Nathaniel under the fig tree, he knew his thoughts (Mk. 2:8) and the disciples even said to him, “you know all things (Jn. 16:30).” These attributes can only be explained if Jesus was in fact all-knowing and all-powerful like God.
Why is it important that Jesus was both fully God and fully man? Let’s first answer the importance of his humanity. Christ is our representative. He is the last Adam (1 Cor. 15:45) whose righteousness leads to our justification and reconciliation (Rom. 5:18-19). Jesus is our substitute. If he didn’t take on human flesh, he couldn’t have died in our place and taken the penalty for our sins. Hebrews 2:16 clarifies this notion: “Therefore he had to be made like his brethren in every respect, so that he might become a merciful and faithful high priest in the service of God, to make expiation for the sins of the people.” Finally, Jesus teaches us how to live. We are to walk in the same way as he walked (1 Jn. 2:6). When we are born again and receive the spirit of God, we receive the mind of Christ and are called to follow him.
Why would Christ have to be God? Only an infinite being is capable of taking the full weight of sin for every human being. Two, God chooses the best plan for salvation, and that is for him to be the hero of the story. He gets to be the Savior, the main actor, the reason why we get to enter heaven. It’s all about the glory of God. I believe that the Christian worldview gives the most glory to God because it’s He who saves, not ourselves.
 Grudem, Systematic Theology, p.532-33.