It is natural for our minds to be drawn to the topic of the Incarnation while considering the Trinity. Athanasius, fourth century bishop of Alexandria, recognized the relationship between these two and dealt with both in the creed bearing his name.
Athanasius concludes the first portion of his creed saying, “He therefore that will be saved must thus think of the Trinity” and immediately begins his defense of the incarnation; “Furthermore it is necessary to everlasting salvation that he also believe rightly the incarnation of our Lord Jesus Christ. For the right faith is that we believe and confess that our Lord Jesus Christ, the Son of God, is God and man.”
The remainder of the creed deals with Christ’s humanity and deity. He affirms that Jesus Christ is true God and true man, two natures in a single person without any confusion of the two. He is careful to lay down the truth that Jesus Christ was of the same substance as the heavenly Father in his deity and of the same substance as his mother according to his humanity. Furthermore, Athanasius refutes the idea that Jesus Christ is an example of man evolving to godhood or of God devolving to man. Instead, in Christ we see God clothed in human flesh.
Moreover, we must not think that in the incarnation God took into union with himself a human person. Christ is not two beings with two centers of self-consciousness. Rather, through the operation of the Holy Spirit the Almighty brought into union with himself a human nature. As a result Jesus Christ is one person with a divine nature and a human nature. This is not to suggest that either nature is somehow impersonal – a mere zombie animated by the presence of the other.
The doctrine of the incarnation can be confusing. Some Christians diminish the deity of Christ and think of him as superhuman rather than true man and true God. Other Christians overlook the humanity of Jesus Christ but still end up making Jesus a superman rather than truly human and truly God. I think the primary reason for these mistakes is the failure to make the proper distinction between Christ’s humanity and his deity. Even then we should be careful that we do not disturb the unity of the person of Christ. As you can see, the doctrine of the incarnation is a mystery just as the doctrine of the Trinity is a mystery.
It is important to acknowledge and understand the humanity of Jesus Christ because our salvation depends upon his being truly human. The Bible tells us that the sacrifice of animals cannot pay for man’s sin. The sin of mankind had to be paid for by someone who is part of the family of man. Hence, Jesus Christ is the “last Adam,” a truly human person who was qualified to pay for the sins of mankind. As the Heidelberg Catechism reminds us, “He must be a true man because the justice of God requires that the same human nature which has sinned should pay for sin” (Question 48). Being sinless he did not have a personal debt of sin which required payment and so his death paid for the sin of others.
Additionally the promises of God were made to the seed of Abraham and to the seed of David. Thereby it is required that he in whom the promises find their fulfillment be the actual seed of Abraham and of David. Thus, the death of this perfect human being is deemed acceptable to God and entered into the books as a propitiation on behalf of anyone who is willing to receive it. Those who do so are forgiven and granted access to all of the covenant promises of God.