To Florus 4.23

For he had also said in his Gospel: “The world was made through him, and the world did not know him” (John 1:10) (Matthew 10:37). He certainly did not mean that the elements, which lack reason, could appear capable of knowing or denying Christ. He meant the multitude of unbelievers to be designated by the name “world.” In the same way here, too, he says that everything in the world—that is, every sort of person so devoted to pleasures that they measure all the goods of a rational creature by the trappings of power, loads of wealth, or the senses—has swollen with hateful pride. This is not from God, meaning it does not please God, but is from the world: it is conceived through the perversity of the human will. “Therefore,” he says in effect, “it must not corrupt you by making you imitate it. Whoever does God’s will comes to share eternal blessedness and does not fly past with the frailty of present things.”

So the apostle John commanded the world to be hated in the same way that the Lord in the Gospel showed that not only our body but even our soul itself must be hated: “Whoever does not hate father or brother, and even his own soul as well, is not worthy of me” (Luke 14:26; compare Matthew 10:37). Yet the mind of a believer certainly cannot hate itself when, out of the most thoughtful love, it purchases its own happiness even through pains and dangers. What, then, have we established? That the apostle John, following Scripture’s custom, struck with the word “world” not the nature of things but the vices of wills. And he denied that the desire of the flesh is from God in the same way that he denied this of everything in the world. Manichaeus seized on this, as though following its logic, but according to his own faithlessness rather than the apostle’s meaning. He asserts that neither the desire of the flesh, nor flesh itself, nor, finally, the whole world was made by God. Following him, you believe that the desire of the flesh was created not by God but by the devil.