The study of Christology is an interesting field because of the uniqueness of the subject. Jesus Christ was such an astounding figure that people not only wondered who he was, but they wondered what he was. However, once we arrive at an answer to these questions, we also need to understand what he was trying to accomplish and the correct ways to speak about him so as to avoid confusion. Every person needs to look at Christ and answer those questions because those questions are fundamental to who we are as human beings and our purpose.
The question of Jesus’s divinity is one that must be seriously considered. There is so much that can be said on this topic, but the key to this claim is the Resurrection and the fruits produced by it. The Resurrection is a concrete event that took place in a specific time and place, and it cements the claim of Jesus’s divinity. All of the Gospels (and the New Testament) provide claims of his divinity in several ways, such as his control of the weather in Matthew or his identity with the Son of Man in Daniel (and many others). Yet, these claims are largely substantiated with the empty tomb. The result of this event is the birth of the Church which spreads in an astounding way that could not have been foreseen because of its apparently ignoble beginning (by the humiliating death of its founder).
Once we accept Christ’s divinity, we are left with another question: what exactly do we mean by that? What is the nature of God who looks like a man and what purpose does it serve? The most reasonable answer is love. Each of us is responsible to maintain truth and righteousness in action and word and our failure to behave in this way is failing to give God what he is owed (Anselm I:11). Thus, we now must make restitution for this wrong. Yet, we already owe God everything we have and are in no position to repay this debt.
It is necessary to understand that sin, in one sense, is failing to give God what is owed. As a matter of justice every creature is responsible to maintain truth and righteousness in both action and word. The failure to act in such a way takes away something from what belongs to God and this must be restored. In a similar way, if a man wrongs his brother it is his duty to restore that which was lost and sin creates an obligation analogous to this. The recompense is proportional to the wrong committed (I:20).
Yet, man already owes God his very being and all that he is able to accomplish. As such, it is not within his power to give God more than this and therefore he is not able to repay this “debt”. When Adam and Eve turned from God they placed themselves and their descendants in such a way that we were gripped within sin and unable to make satisfaction. Mankind is responsible to repay this for otherwise he is not making recompense (II:6). This being the case, we arrive at an impasse: mankind must repay his debt, but he does not possess the power to do so.
Although man had turned away, the love of the Word was not diminished, and He came among men to redeem them (Athanasius 4). Men had lost the grace that God had offered, and they reverted to the nature of the finite, which does not last forever. Yet, as time went on, they turned further and further from God's love, giving in to their insatiable appetites. In order that we may no longer be slaves to our passion and once more make God known to Us Christ "assumed humanity that we might become God" (Athanasius 54). God in his love and mercy freely chose to become a man. The second person of the Trinity assumes the form of the God-man. Further, he assumes the nature of man while doing no injury to His Divine nature, perfectly God and perfectly man.
As a member of the human race, he is now able to make recompense for his fellow man, but as a Divine Person he still has the power to pay it (Anselm II:8). In order to make this recompense, He must offer something either from himself or himself (II:11). All sins “which are directed elsewhere than against the person of God, can be regarded as equal” in no way to the life of Christ (II: 14). When Christ lays down his life, voluntarily, he makes an offering of infinite value for the redemption of mankind. He accepts death which outweighs all the sins of mankind and restored the destiny of man which had been lost. He offers his life, which is of infinite value, for our redemption. He accepts his own death which outweighs our sins and restores us. Thus, the Second Person of the Trinity is fully God and fully man. Fully God so he is able to pay the price and fully man so that he shares in our debt. He gives himself completely for us out of love and merits for us the grace which we need to return that love.
These two natures, human and divine, and united in the single person of Christ. This point is of extreme importance to make sense of the passion and redemption of mankind. Christ is not half god, half man or a mixture of two natures into some different kind of thing. He is not merely a man adopted as God nor a divine being without trace of humanity. In order to help make this more intelligible we rely on the communication idiomatum. This means that when speaking of Christ we can predicate properties of either nature to the person. This does not mean that the properties of one nature belong to the other, but the Second Person of the Trinity possesses each nature. This precision in language aids in understanding the Incarnation and the Redemption and provides the structure for understanding how we can speak of God being born or dying.
Christ has merited a great gift which he bestows on each of us although we have done nothing to deserve it (II: 19). The second person of the Trinity became man to restore us to friendship with God and satisfy justice. His mercy is boundless, so much so, that the Son offers himself to redeem our trespass although he lacks any guilt whatsoever (II:20). As Anselm says, “What… can be conceived of more merciful than that God the Father should say to a sinner condemned to eternal torments… ‘Take my only-begotten Son and give him on your behalf’” (II: 20).
God has freely given himself to each us by an act of will. He becomes Incarnate, uniting himself to our humanity, and offering Himself for our redemption. He shows us what it means to be the perfect image of God so we may love God and neighbor. There is no matter more important to integrate into our lives than the love of God which then allows us to love our neighbor more perfectly.
St. Athanasius. On the Incarnation. St. Athanasius: On the Incarnation of the Word - Christian Classics Ethereal Library, https://ccel.org/ccel/athanasius/incarnation/incarnation.i.html.
Canterbury, Anselm. Anselm of Canterbury: The Major Works. Oxford University Press, 2008.