18a.2 Boso. You have satisfied me that it cannot be proved that he was subjected to death by any necessity 278; and I cannot regret my importunity in urging you to make this explanation.
Anselm. I think we have shown with sufficient clearness how it was that God took a man without sin from a sinful substance; but I would on no account deny that there is no other explanation than this which we have given, for God can certainly do what human reason cannot grasp. But since this appears adequate, and since in search of other arguments we should involve ourselves in such questions as that of original sin, and how it was transmitted by our first parents to all mankind, except this man of whom we are speaking; and since, also, we should be drawn into various other questions, each demanding its own separate consideration; let us be satisfied with this account of the matter, and go on to complete our intended work.
Boso. As you choose; but with this condition that, by the help of God, you will sometime give this other explanation, which you owe me, as it were, but which now you avoid discussing.
Anselm. Inasmuch as I entertain this desire myself, I will not refuse you; but because of the uncertainty of future events, I dare not promise you, but commend it to the will of God. But say now, what remains to be unravelled with regard to the question which you proposed in the first place, and which involves many others with it?
Boso. The substance of the inquiry was this, why God became man, for the purpose of saving men by his death, when he could have done it in some other way. And you, by numerous and positive reasons, have shown that the restoring of mankind ought not to take place, and could not, without man paid the 279debt which he owed God for his sin. And this debt was so great that, while none but man must solve the debt, none but God was able to do it; so that he who does it must be both God and man. And hence arises a necessity that God should take man into unity with his own person; so that he who in his own nature was bound to pay the debt, but could not, might be able to do it in the person of God. In fine, you have shown that that man, who was also God, must be formed from the virgin, and from the person of the Son of God, and that he could be taken without sin, though from a sinful substance. Moreover, you have clearly shown the life of this man to have been so excellent and so glorious as to make ample satisfaction for the sins of the whole world, and even infinitely more. It now, therefore, remains to be shown how that payment is made to God for the sins of men.
Source: Cur Deus Homo (CCEL)