Let’s start with Cicero’s understanding of natural law, which seems to be the touchstone for his discussion of politics and ethics. Cicero believed that a rational Providence oversaw the universe — a universe embedded in divine law, or a set of moral and religious truths that govern the human condition. This was the basis for all sound civil law. “The nature of law must be sought in the nature of man,” he wrote in The Laws. “Man is a single species which has a share in divine reason and is bound together by a partnership in justice.”

A political commitment to justice, according to Cicero, was only possible because of the universal and immutable character of natural law. It alone provided “the bond which holds together a community of citizens”:

We cannot be exempted from this law by any decree of the Senate or the people; nor do we need anyone else to expound or explain it. There will not be one such law in Rome and another in Athens, one now and another in the future, but all peoples at all times will be embraced by a single and eternal and unchangeable law; and there will be, as it were, one lord and master of us all — the god who is the author, proposer and interpreter of that law. Whoever refuses to obey it will be turning his back on himself. Because he has denied his nature as a human being he will face the gravest penalties for this alone.

It’s worth remembering that the Anglo-American political tradition — from John Locke to James Madison — owes a profound debt to the natural law philosophy that can be traced to Cicero. Without a belief in “the Moral Law”, there would have been no argument for the “inalienable rights” of every human being. Without natural law, there was no foundation for a political community based on equal justice. Whoever refuses to obey it will be turning his back on himself.

Today, of course, the natural law tradition has been discarded by Western liberal elites. And what have been the results? Cicero might have predicted them, based on what he had to say about the moral trajectory of Rome. There were staggering social injustices, and little regard for the common good; factions were the order of the day. “Nothing can be sweeter than liberty,” he wrote. “Yet if it isn’t equal throughout, it isn’t liberty at all.”

Is there any more conspicuous feature of contemporary democracies — especially the United States — than the denigration of the idea of the common good? The breakdown in a “partnership in justice” is nearly complete.

For Cicero, the great symptom of decline was Rome’s ongoing crisis in political leadership. By rejecting natural law — and its ability to both restrain vice and inspire virtue — Rome’s leaders behaved as though their “private lives” bore no relationship to the public good. The wrong kinds of men were entering politics for all the wrong reasons. Thanks to a “vulgar misconception,” Cicero wrote, “a few with money, not worth, have gained control of the state.” Welcome to American political culture on the eve of a presidential election.