When to this natural basis of custom a supernatural sanction is added by religion, and the ways of one’s ancestors are also the will of the gods, then custom becomes stronger than law, and subtracts substantially from primitive freedom. To violate law is to win the admiration of half the populace, who secretly envy anyone who can outwit this ancient enemy; to violate custom is to incur almost universal hostility. For custom rises out of the people, whereas law is forced upon them from above; law is usually a decree of the master, but custom is the natural selection of those modes of action that have been found most convenient in the experience of the group.

Law partly replaces custom when the state replaces the natural order of the family, the clan, the tribe, and the village community; it more fully replaces custom when writing appears, and laws graduate from a code carried down in the memory of elders and priests into a system of legislation proclaimed in written tables. But the replacement is never complete; in the determination and judgment of human conduct custom remains to the end the force behind the law, the power behind the throne, the last “magistrate of men’s lives.”

- Will Durant, Our Oriental Heritage