Why God became man
Anselm's Cur Deus Homo
Anselm has become Archbishop of Canterbury — a position he never wanted and from which he was twice exiled by English kings who found him inconvenient. He writes his most important theological work, Cur Deus Homo — Why God Became Man — during one of these exiles.
The question he is answering is the question Anselm frames as: could God not simply have forgiven human sin by a declaration, without the incarnation and crucifixion? Why did salvation require the death of the Son of God?
His answer develops what becomes the satisfaction theory of atonement: sin is an offense against the infinite honor of God. The debt incurred is therefore infinite. An infinite debt requires an infinite payment. Only God can make an infinite payment. But the debt is human — owed by humanity, not by God. Therefore only a being who is both God and human can pay the debt.
The conclusion is the incarnation: not an arbitrary arrangement but a logical necessity. Given what sin is and what God is and what humanity is, the incarnation and crucifixion are the only possible resolution.
Cur Deus Homo is not the only account of the atonement — the New Testament uses many images — but it becomes the dominant framework in Western theology, shapes the Reformation doctrine of justification, and is still the most-discussed theory of how the cross accomplishes what the gospel claims it accomplishes.
Anselm writes it in exile. He is always more productive when kings are making his life difficult.
“What could be more merciful than that God the Father should say to a sinner condemned to eternal torments, and lacking any means of redeeming himself: Take my only-begotten Son and offer him on your behalf?”
— Anselm, Cur Deus Homo II.20, c. 1098 AD
“whom God set forth to be an atoning sacrifice, through faith, in his blood, to show his righteousness because of the passing over of the sins done before, in the forbearance of God; for the showing of his righteousness at this present time; that he might himself be just, and the justifier of him who has faith in Jesus.”
Anselm asks: why did salvation require the death of God? And he works out an answer that takes both sin and grace with full seriousness.
The debt is real. The honor is real. The requirement is real. And the mercy is real — so real that God himself pays what only God could pay, in the only form that could pay it.
The cross is not arbitrary. It is the precise, logical, inevitable response to the precise, logical, inevitable problem of what sin actually is and what God actually is.
When you contemplate the cross, do you contemplate it as something that had to happen — as the only possible resolution to the precise weight of what was owed — or as a vague gesture of divine goodwill?
Anselm invites you to think it through until the weight of it is real.