As is well known this is the title of Anselm of Canterbury’s famous treatise on why God became man. Anselm sought to demonstrate the truth of the Incarnation on grounds independent from specifically Christian texts. This was probably due to some of his more prominent opponents were educated Jews who did not accept the New Testament as a source of revealed information. (See R.W. Southern, Anselm: A Portrait in a Landscape) The upshot is that God became man in response to the fall because humans could never make satisfaction, where satisfaction has a precise theological meaning for Anselm. In other words, Anselm wasn’t advocating a penal model of the atonement.
But what if the Fall had never occurred? Would Christ still have become incarnate anyway? If so, what purpose could it serve? If Christ were to become incarnate without a fall, doesn’t this leave the incarnation as an explanatory dangler, not to mention the Cross?
Among Western theologians the answers are diverse but they all tend to be rather speculative. Albert the Great for example states
“On this question it must be said that the solution is uncertain, but insofar as I can express an opinion, I believe that the Son of God would have been made man, even if sin had never been.” (Senteniarum, dist.20, art. 4.)
John Duns Scotus comes to a similar though more robust conclusion,
“I say, nevertheless, that the Fall is not the cause Christ’s predestination. Indeed, even if one angel had not fallen, or one man, Christ would still have been predestined thus-even if others had not been created, but only Christ.” (Opus Oxoniense, 3, dist 19.)
Note the way that Scotus speaks of the predestination of Christ. Scotus seems to endorse then a fully supralapsarian Christology. This is probably the strongest theoretical form that an answer in the affirmative can take. It is not just that Christ would have become incarnate apart from the Fall, but even apart from Creation. As Florovksy notes
“The whole question for Duns Scotus was precisely that of the order of Divine ‘predestination’ or purpose, i.e. of the order of thoughts in the Divine counsel of Creation. Christ, the incarnate, was the first object of the creative will of God, and it was for Christ’s sake that anything else had been created at all.” (Creation and Redemption, 165)
Aquinas on the other hand, while sympathetic to the affirmative answer, replies somewhat in the negative.
“Hence, since everywhere in the Sacred Scripture the sin of the first man is assigned as the reason of Incarnation, it is more in accordance with this to say that the work of Incarnation was ordained by God as a remedy for sin; so that, had sin not existed, Incarnation would not have been.” (ST 3, q. 1, art. 3 )
In the commentary on the Sentences Aquinas appears more cautious claiming that only Christ knows the answer to the question. (3 Senten., dist. 1, q. 1, art.3.) Bonaventure while similarly cautious took the negative as more appropriate or agreeable to piety. In the 17th century there was a flurry of discussion between Catholics and Protestants. The great Jesuit Robert Bellermine wrote,
“For if Adam had remained in that innocence wherein he had been created, doubtless the Son of God would not have suffered: He probably would not even have assumed human flesh, as Calvin himself teaches.” (De Christo, lib 5, cap 10)
To my knowledge Rome has left the question unanswered and undefined in any authoritative way. Without a doubt it is true that God becomes man to redeem humanity from sin, death and the devil. I think a worry that some have had is that if the Incarnation would have occurred anyway that this somehow diminishes divine love for humanity in redemption or makes the work of Christ somehow less important. I don’t think this is the case and I think that worry can be assuaged.
Often though, textbooks make the claim that the Fathers never address this question or teach clearly or definitively on it. Certainly the Fathers don’t appear to address the question in this form but it is misleading to conclude that the matter is left untouched in any definitive way in the patristic corpus. St. Maximus the Confessor is quite clear that God at all times wills the mystery of his Incarnation. God’s eternal purpose has been to unite the cosmos with himself. God has eternally willed to dwell with his people. God eternally wills the eternal existence of his creation. (Ambiguum 7:2) This is how Maximus understands such passages as Matt 25:34, Eph 1:9, and 1 Pet 1:20. )
What then are we to make of the Fall and the Cross? The interesting thing is that Maximus’ teaching reorients us to them in an illuminating way. Instead of the Incarnation being a response to sin and death, the order is turned around. The Fall was an attempt by the devil to prevent the Incarnation. Since God eternally wills his incarnation, to prevent its occurrence would be to frustrate the divine will and demonstrate the devil’s superiority. So the temptation and the Fall are a response to the Incarnation.
Looking at the Incarnation this way puts God back in the driver’s seat. It also accentuates the biblical material on the role of the devil as destroyer, lord of decay or corruption (Beelzebub) and a murderer from the beginning. It explains why the devil hates the human race so much and so desperately tries to find ways to maximize sin throughout human history to annihilate it. It is a blinding rage. The thief comes to steal, kill and destroy, but Christ comes that we might have life! Christ’s generosity of life is so much greater than the sin of man that he even gives immortal life to those who deny him. (2 Pet 2:1) so that he is the savior of all men, but even more so of those who believe. (1 Tim 4:10) Consequently, the vindication or justification of life came to all men by Christ. (Romans 5:18). It broadens the redemptive work of Christ making it truely cosmic in scope in a way more faithful to the Pauline vision. (Rom 8:22, Eph 1:10)
The death of Christ is an undying death. It is not a death where the person suffers death in such a way where the death lays hold of them, but the other way around. Christ goes into death actively taking hold of it. As the paschal liturgy proclaims, he tramples down death by death. He victoriously maintains the hypostatic union between humanity and divinity by his divine power. God is truly pleased in the faithful Son who vindicates or justifies his Father’s name trampling down his enemies. Jesus glorifies his Father’s name. Christ holds the keys of death and Hades so that not even death can frustrate the divine will for the everlasting man.