13. Let us then return to the words, which I had set forth out of the Apostle as obscure, and we shall now see them to be plain. For this I had set forth, that the Apostle did not say, “Walk in the Spirit, and ye shall not have the lusts of the flesh;” because we must necessarily have them. Why then did he not say, “Ye shall not do the lusts of the flesh”? Because we do them; for we do lust. The very lusting, is doing. But the Apostle says, “Now it is no more I that do it, but sin that dwelleth in me.” What then hast thou to beware of? This doubtless, that thou fulfil them not. A damnable lust hath risen up, it hath risen, made its suggestion; let it not be heard. It burneth, and is not quieted, and thou wouldest that it should not burn. Where then is, “So that ye cannot do the things that ye would”? Do not give it thy members. Let it burn without effect, and it will spend itself. In thee then these lusts are done. It must be confessed, they are done. And therefore he said, “Ye shall not fulfil.” Let them not then be fulfilled. Thou hast determined to do, thou hast fulfilled. For thou hast fulfilled it, if thou determinest upon committing adultery, and dost not commit it, because no place hath been found, because no opportunity is given, because, it may be, she for whom thou seemest to be disturbed is chaste; lo, now she is chaste, and thou art an adulterer. Why? Because thou hast fulfilled lusts. What is, “hast fulfilled”? Hast determined in thy mind upon committing adultery. If now, which God forbid, thy members too have wrought, thou hast fallen down headlong into death.