This is an excerpt from Athanasius’ work, entitled On the Incarnation of the Word. Here he describes one of the reasons for the incarnation:1
§ 6. The human race then was wasting, God’s image was being effaced, and His work ruined. Either, then, God must forego His spoken word by which man had incurred ruin; or that which had shared in the being of the Word must sink back again into destruction, in which case God’s design would be defeated. What then? Was God’s goodness to suffer this? But if so, why had man been made? It would have been weakness, not goodness on God’s part.
For this cause, then, death having gained upon men, and corruption abiding upon them, the race of man was perishing; the rational man made in God’s image was disappearing, and the handiwork of God was in process of dissolution.
For death, as I said above, gained from that time forth a legal hold over us, and it was impossible to evade the law, since it had been laid down by God because of the transgression, and the result was in truth at once monstrous and unseemly.
For it were monstrous, firstly, that God, having spoken, should prove false—that, when once He had ordained that man, if he transgressed the commandment, should die the death, after the transgression man should not die, but God’s word should be broken. For God would not be true, if, when He had said we should die, man died not.
Again, it were unseemly that creatures once made rational, and having partaken of the Word, should go to ruin, and turn again toward non-existence by the way of corruption. For it were not worthy of God’s goodness that the things He had made should waste away, because of the deceit practised on men by the devil. Especially it was unseemly to the last degree that God’s handicraft among men should be done away, either because of their own carelessness, or because of the deceitfulness of evil spirits.
So, as the rational creatures were wasting and such works in course of ruin, what was God in His goodness to do? Suffer corruption to prevail against them and death to hold them fast? And where were the profit of their having been made, to begin with? For better were they not made, than once made, left to neglect and ruin. For neglect reveals weakness, and not goodness on God’s part—if, that is, He allows His own work to be ruined when once He had made it—more so than if He had never made man at all. For if He had not made them, none could impute weakness; but once He had made them, and created them out of nothing, it were most monstrous for the work to be ruined, and that before the eyes of the Maker.
It was, then, out of the question to leave men to the current of corruption; because this would be unseemly, and unworthy of God’s goodness.
§ 7. On the other hand there was the consistency of God’s nature, not to be sacrificed for our profit. Were men, then, to be called upon to repent? But repentance cannot avert the execution of a law; still less can it remedy a fallen nature. We have incurred corruption and need to be restored to the grace of God’s Image. None could renew but he who had created. He alone could (1) recreate all, (2) suffer for all, (3) respect all to the Father.
But just as this consequence must needs hold, so, too, on the other side the just claims of God lie against it: that God should appear true to the law He had laid down concerning death. For it were monstrous for God, the Father of truth, to appear a liar for our profit and preservation.
So here, once more, what possible course was God to take? To demand repentance of men for their transgression? For this one might pronounce worthy of God; as though, just as from transgression men have become set towards corruption, so from repentance they may once more be set in the way of incorruption.
But repentance would, firstly, fail to guard the just claim of God. For He would still be none the more true, if men did not remain in the grasp of death; nor, secondly, does repentance call men back from what is their nature—it merely stays them from acts of sin.
Now, if there were merely a misdemeanour in question, and not a consequent corruption, repentance were well enough. But if, when transgression had once gained a start, men became involved in that corruption which was their nature, and were deprived of the grace which they had, being in the image of God, what further step was needed? Or, what was required for such grace and such recall, but the Word of God, which had also at the beginning made everything out of nought?
For His it was once more both to bring the corruptible to incorruption, and to maintain intact the just claim of the Father upon all. For being Word of the Father, and above all, He alone of natural fitness was both able to recreate everything, and worthy to suffer on behalf of all and to be ambassador for all with the Father.
§ 8. The Word, then, visited that earth in which He was yet always present; and saw all these evils. He takes a body of our Nature, and that of a spotless Virgin, in whose womb He makes it His own, wherein to reveal Himself, conquer death, and restore life
For this purpose, then, the incorporeal and incorruptible and immaterial Word of God comes to our realm, howbeit he was not far from us before. For no part of Creation is left void of Him: He has filled all things everywhere, remaining present with His own Father. But He comes in condescension to shew loving-kindness upon us, and to visit us.
And seeing the race of rational creatures in the way to perish, and death reigning over them by corruption; seeing, too, that the threat against transgression gave a firm hold to the corruption which was upon us, and that it was monstrous that before the law was fulfilled it should fall through: seeing, once more, the unseemliness of what was come to pass: that the things whereof He Himself was Artificer were passing away: seeing, further, the exceeding wickedness of men, and how by little and little they had increased it to an intolerable pitch against themselves: and seeing, lastly, how all men were under penalty of death …
He took pity on our race, and had mercy on our infirmity, and condescended to our corruption, and, unable to bear that death should have the mastery—lest the creature should perish, and His Father’s handiwork in men be spent for nought—He takes unto Himself a body, and that of no different sort from ours.
For He did not simply will to become embodied, or will merely to appear. For if He willed merely to appear, He was able to effect His divine appearance by some other and higher means as well. But He takes a body of our kind, and not merely so, but from a spotless and stainless virgin, knowing not a man, a body clean and in very truth pure from intercourse of men.
For being Himself mighty, and Artificer of everything, He prepares the body in the Virgin as a temple unto Himself, and makes it His very own as an instrument, in it manifested, and in it dwelling.
And thus taking from our bodies one of like nature, because all were under penalty of the corruption of death He gave it over to death in the stead of all, and offered it to the Father—doing this, moreover, of His loving-kindness, to the end that, firstly, all being held to have died in Him, the law involving the ruin of men might be undone (inasmuch as its power was fully spent in the Lord’s body, and had no longer holding-ground against men, his peers), and that, secondly, whereas men had turned toward corruption, He might turn them again toward incorruption, and quicken them from death by the appropriation of His body and by the grace of the Resurrection, banishing death from them like straw from the fire.
§ 9. The Word, since death alone could stay the plague, took a mortal body which, united with Him, should avail for all, and by partaking of His immortality stay the corruption of the Race. By being above all, He made His Flesh an offering for our souls; by being one with us all, He clothed us with immortality. Simile to illustrate this.
For the Word, perceiving that no otherwise could the corruption of men be undone save by death as a necessary condition, while it was impossible for the Word to suffer death, being immortal, and Son of the Father; to this end He takes to Himself a body capable of death, that it, by partaking of the Word Who is above all, might be worthy to die in the stead of all, and might, because of the Word which was come to dwell in it, remain incorruptible, and that thenceforth corruption might be stayed from all by the Grace of the Resurrection.
Whence, by offering unto death the body He Himself had taken, as an offering and sacrifice free from any stain, straightway He put away death from all His peers by the offering of an equivalent.
For being over all, the Word of God naturally by offering His own temple and corporeal instrument for the life of all satisfied the debt by His death. And thus He, the incorruptible Son of God, being conjoined with all by a like nature, naturally clothed all with incorruption, by the promise of the resurrection.
For the actual corruption in death has no longer holding-ground against men, by reason of the Word, which by His one body has come to dwell among them. And like as when a great king has entered into some large city and taken up his abode in one of the houses there, such city is at all events held worthy of high honour, nor does any enemy or bandit any longer descend upon it and subject it; but, on the contrary, it is thought entitled to all care, because of the king’s having taken up his residence in a single house there: so, too, has it been with the Monarch of all.
For now that He has come to our realm, and taken up his abode in one body among His peers, henceforth the whole conspiracy of the enemy against mankind is checked, and the corruption of death which before was prevailing against them is done away. For the race of men had gone to ruin, had not the Lord and Saviour of all, the Son of God, come among us to meet the end of death.
1 Athanasius of Alexandria, “On the Incarnation of the Word,” in NPNF2, vol. 4, ed. Philip Schaff and Henry Wace, trans. Archibald T. Robertson (New York, NY: Christian Literature Company, 1892), § 6 - 9.