St. John Chrysostom: "The law which God ingrafted in man"

“WE use not only Scripture but also reason in arguing against the pagans. What is their argument? They say they have no law of conscience, and that there is no law implanted by God in nature. My answer is to question them about their laws concerning marriage, homicide, wills, injuries to others, enacted by their legislators. Perhaps the living have learned from their fathers, and their fathers from their fathers and so on. But go back to the first legislator! Was it not by his own conscience and conviction? Nor can it be said that they heard Moses and the prophets, for Gentiles could not hear them. It is evident that they derived their laws from the law which God ingrafted in man from the beginning.”

~St. John Chrysostom: Ad pop. Ant., XII, 4.

See also:
• Romans 2:12-15
• St. John Chrysostom: Homilies on the Epistle to the Romans, Homily V

Byzantine mosaic of St. John Chrysostom from the Hagia Sophia