To Florus 1.69

“To arrive at this mention of human misery and divine grace, the apostle had said earlier: ‘I see another law in my members, fighting against the law of my mind and taking me captive in the law of sin’ (Romans 7:23). After these words he exclaimed: ‘Who will rescue me from the body of this death? God's grace through Jesus Christ our Lord’” (Romans 7:24–25). It is indeed established that after the preceding words you quoted, the apostle added: “Wretched man that I am! Who will rescue me from the body of this death? God's grace through Jesus Christ our Lord.” But at present we are not asking whether the apostle said this. We are asking with what belief, meaning, and reasoning he said it. By the law in his members he meant an evil habit that, through the practice of shameful deeds, rebels against holy intentions, at least in the beginning of amendment. Even learned people of this world commonly call habit a second nature.

A little earlier, addressing his readers reproachfully, he had said: “I speak in human terms because of the weakness of your flesh. Just as you presented your members to serve impurity and lawlessness leading to lawlessness, so now present your members to serve righteousness leading to sanctification” (Romans 6:19). To show that by “flesh” he figuratively meant vices, not this body whose causes lie in seed, he adds perhaps two passages later: “When we were in the flesh, the passions of sins which are disclosed through the Law worked in our members to bear fruit for death” (Romans 7:5). He said, “When we were in the flesh”, as though he were not in the flesh at the time he was speaking. But whoever knows Scripture recognizes this manner of expression. Where a shared use of words creates a difficulty, therefore, apply the rule of reason, and let what seemed bent be straightened against its level.

Faustus, bishop of the Manichaeans and your teacher, relies especially on this testimony of the apostle against us. He says that by these words about a law dwelling in the members and resisting the mind's purpose, the apostle meant nothing other than an evil nature. Nothing, therefore, was less appropriate for you than to understand this passage as they explain it. Otherwise, as you follow the same twisted lines Faustus drew, you seem not to have argued a case but to have recited old lessons.