St. Athanasius composed one of the most important books in Christian literature, On the Incarnation, which provides a discourse on the divinity of Christ and the redemptive purpose of the Incarnation. In explaining the reason behind the Word of God becoming man, St. Athanasius provides five main arguments; in this article, we will cover the first of these.

The Incarnation is the only possible sacrifice to redeem humans from their original sin.

St. Athanasius argues that it was not possible for God to just forgive man when he sinned and not let him die because “it would, of course, have been unthinkable that God should go back upon His word and that man, having transgressed, should not die.” He also excluded the possibility for God to let man perish because “it was equally monstrous that beings which once had shared the nature of the Word should perish and turn back again into non-existence through corruption”. He defended this assumption by arguing that “such indifference to the ruin of His own work before His very eyes would argue not goodness in God but limitation… It was impossible, therefore, that God should leave man to be carried off by corruption, because it would be unfitting and unworthy of ‎Himself.”‎

St. Athanasius went on to exclude a third possibility, which is simply repentance ‎of man, because it “would not guard the Divine consistency, for, if death did not hold dominion over men, God would still remain untrue.” As such, the incarnation and sacrifice of our Lord Jesus Christ as the Word of God was essential to “maintain for the Father His consistency of character with all.”‎

After excluding the three alternatives of forgiveness without sacrifice, perishing of man, or mere repentance of man, St. Athanasius then argues that the infinite sacrifice of the Word of God has universal redemptive effect because “in His death all might die, and the law of death thereby be abolished because, having fulfilled in His body that for which it was appointed, it was thereafter voided of its power for men.”‎

Since the Incarnation of the Word of God was essential,

“He assumed a body capable of death, in order that it, through belonging to the Word who is above all, might become in dying a sufficient exchange for all, and, itself remaining incorruptible through His indwelling, might thereafter put an end to corruption for all others as well, by the grace of the resurrection.” ‎

St. Athanasius concluded the argument on the ransom paid by Christ by stating that “it was by surrendering to death the body which He had taken, as an offering and sacrifice free from every stain, that He forthwith abolished death for His human brethren by the offering of the equivalent.”‎

However, later in the book, St. Athanasius recognised a possible objection to his first argument, since we still die, even Christians go through the same death punishment due to the original sin. To this objection, St. Athanasius explained the effect of the redemption of Christ:

“When we die, we no longer do so as men condemned to death, ‎but as those who are even now, in the process of rising, we await the general resurrection of ‎all.”‎