To Florus 3.188

It remains to examine your statement which, promising to reduce it to one expression, you gathered up briefly—and, it must be admitted, rather cleverly: ‘If human nature were evil, it should not be generated; if it had no evil, it should not be regenerated. To sum up both in one word: if human nature were evil, it ought not to be saved; if no evil were within it, it would not need to be saved’ (Augustine, Marriage and Sexual Desire 2.36).

Here you must not be cheated of praise for your intelligence. From your standpoint it could not have been said better. Yet the nature of things prevents even precise cunning from accomplishing anything. It is altogether hard for you to kick against the goad (Acts 26:14). Whatever you put together melts like ice when the fire of truth is brought near. Now attend to our reply. You concluded: ‘Surely if human nature were evil, it ought not to be saved.’ We agree; you spoke entirely truly. If it were evil, it ought not to be saved, because something evil by nature would neither deserve nor be capable of salvation. Why incapable? Because it could not become other than it had been made. Why undeserving? Because nothing in it would be worthy of deliverance by God’s mercy.

When we say ‘if it were’ about what certainly cannot exist, we are not giving hope that the denied possibility can occur. Rather, to destroy another opinion that arises, we commonly speak about impossible things. For example: If this or that existed, that consequence would undoubtedly follow. Since the first cannot exist, the conclusion introduced in order to remove it is denied all the more. We have already shown frequently that nothing can be evil by nature. Nevertheless, without prejudice to that settled point, we now approve the part of your statement saying, ‘If human nature were evil, it ought not to be saved.’

You located salvation in baptism and argued consistently that if the Manichaeans, who call nature evil, spoke truly, Christians would be foolish to believe baptism’s remedy should be applied to an evil nature. Thus anyone affirming that human nature is evil is forced to deny grace. This also works in reverse: anyone affirming grace praises human nature, understanding grace to have been provided for its salvation.