power to prevent, attaches the blame of what happens. We say to them, that causation is seen in doing, working, acting; but the not preventing is in this respect inoperative. Further, causation attaches to activity; as in the case of the shipbuilder in relation to the origin of the vessel, and the builder in relation to the construction of the house. But that which does not prevent is separated from what takes place. Wherefore the effect will be accomplished; because that which could have prevented neither acts nor prevents. For what activity does that which prevents not exert? Now their assertion is reduced to absurdity, if they shall say that the cause of the wound is not the dart, but the shield, which did not prevent the dart from passing through; and if they blame not the thief, but the man who did not prevent the theft. Let them then say, that it was not Hector that burned the ships of the Greeks, but Achilles; because, having the power to prevent Hector, he did not prevent him; but out of anger (and it depended on himself to be angry or not) did not keep back the fire, and was a concurring cause. Now the devil, being possessed of free-will, was able both to repent and to steal; and it was he who was the author of the theft, not the Lord, who did not prevent him. But neither was the gift hurtful, so as to require that prevention should intervene.
But if strict accuracy must be employed in dealing with them, let them know, that that which does not prevent what we assert to have taken place in the theft, is not a cause at all; but that what prevents is involved in the accusation of being a cause. For he that protects with a shield is the cause of him whom he protects not being wounded; preventing him, as he does, from being wounded. For the demon of Socrates was a cause, not by not preventing, but by exhorting, even if (strictly speaking) he did not exhort. And neither praises nor censures, neither rewards nor punishments, are right, when the soul has not the power of inclination and disinclination, but evil is involuntary. Whence he who prevents is a cause; while he who prevents not judges justly the soul's choice. So in no respect is God the author of evil. But since free choice and inclination originate sins,
