How other angels cannot take the place of those who fell.
Boso. Why could not they themselves be restored, or other angels substituted for them?
Anselm. When you shall see the difficulty of our restoration, you will understand the impossibility of theirs. But other angels cannot be substituted for them on this account (to pass over its apparent inconsistency with the completeness of the first creation), because they ought to be such as the former angels 212would have been, had they never sinned. But the first angels in that case would have persevered without ever witnessing the punishment of sin; which, in respect to the others who were substituted for them after their fall, was impossible. For two beings who stand firm in truth are not equally deserving of praise, if one has never seen the punishment of sin, and the other forever witnesses its eternal reward. For it must not for a moment be supposed that good angels are upheld by the fall of evil angels, but by their own virtue. For, as they would have been condemned together, had the good sinned with the bad, so, had the unholy stood firm with the holy, they would have been likewise upheld. For, if, without the fall of a part, the rest could not be upheld, it would follow, either that none could ever be upheld, or else that it was necessary for some one to fall, in order by his punishment to uphold the rest; but either of these suppositions is absurd. Therefore, had all stood, all would have been upheld in the same manner as those who stood; and this manner I explained, as well as I could, when treating of the reason why God did not bestow perseverance upon the devil.
Boso. You have proved that the evil angels must be restored from the human race; and from this reasoning it appears that the number of men chosen will not be less than that of fallen angels. But show, if you can, whether it will be greater.
Source: Cur Deus Homo (CCEL)