To Florus 3.185

You say: ‘Anyone who has lawful intercourse through desire uses an evil well’ (Augustine, Marriage and Sexual Desire 2.36). You remind us to believe instead the apostle, who said good did not dwell in his flesh, and you want what is not good—that is, the evil dwelling in the apostle’s flesh—to be understood as fleshly desire (Romans 7:18). Mani put it no differently. After saying, ‘So that their deeds will not be exposed,’ he adds: ‘This is why the apostle cries to the Romans: “I do not do the good I want, but I perform the evil I abhor” (Romans 7:19) (John 3:20). He grieved because sin—that is, the devil—produced every desire in him (Romans 7:8). The law’s authority shows desire’s evil by condemning every use of it, which the flesh admires and praises.’