During the Sept. 26 presidential debate between the two major-party candidates, Hillary Clinton and Donald Trump, Clinton made two specific allegations against her opponent. First, she intimated that Trump has at least on occasion failed to pay any federal income taxes (an allegation that was supported over the week by a New York Times report). Trump responded not by challenging her claim’s factual validity, nor with a sense of shame about not paying income taxes. Rather, he proclaimed, “That makes me smart.”

Second, Clinton alleged that in the course of his business career, Trump has regularly failed to pay contractors for work performed, or at least not as much as the amount agreed in signed contracts: “You wouldn’t pay what the man needed to be paid, what he was charging you to do.” Again, Mr. Trump’s response was not to deny the facts or express regret, but rather to suggest that he was not bound by the contracts: “Maybe he didn’t do a good job, and I was unsatisfied with his work.”

Clinton’s accusations are based on numerous media reports.

Trump was unwittingly echoing Plato’s villain Thrasymachus

Remarkably, Trump’s defense presents precisely the benefits of a lifestyle embraced by Plato’s villain from his “Republic,” Thrasymachus. Plato introduces him after having navigated Socrates through civil conversations with others about the nature of justice. By contrast, Thrasymachus is portrayed as an animal, quick to anger and unable to control his own emotions. He departs from what the others consider decent and respectable, as they insist that justice requires paying one’s debts and always speaking the truth. He does not hesitate to suggest that Socrates is an infant who requires a wet nurse, rather than a serious intellectual rival. Were he to have access to Twitter, one could easily imagine Thrasymachus engaging furiously in late-night tweet battles.

Thrasymachus defends the life of the unjust over that of the just because it is more profitable and pleasurable. Specifically, he cites two instances where the unjust life proves superior — and in ways strikingly similar to Trump’s own habits. First, “when there is an income tax, the just man will pay more and the unjust less on the same amount of income.” And second, “in private contracts . . . wherever the unjust is the partner of the just you will find that, when the partnership is dissolved, the unjust man has always more and the just less.” Thus the “smart” person, as Trump might have it, would be wise to avoid paying taxes and fulfilling contractual agreements wherever it is possible to do so with impunity. It is not difficult to recognize the Thrasymachian echoes in last week’s debate.

Thrasymachus’s arguments in Plato’s “Republic” are part of a larger worldview that individuals ought to disregard any pretense of moral or political obligation, objectively understood, if they inhibit our own success. Rather, the priority should always be to acquire as much as possible, maximizing one’s own personal happiness.

Plato criticized Thrasymachus’s philosophy as “pleonexia — the condition of insatiable appetites, whereby the satisfaction of one’s own interests assumes the status of a highest good. The burden of pleonexia, for Plato, is that it can never be satisfied. There is no amount of money that ever constitutes “enough.” There is no amount of public praise that is enough. It is a quest that reaches its summit in becoming a political tyrant.

Plato warned that this attitude can lead a public person to become a tyrant

But as Plato’s Socrates warns subsequently in Book 9 of “The Republic,” even acquiring this kind of power fails to satisfy pleonexia’s demands. In fact, it only intensifies the miseries both of the ruler and his subjects. The citizens live in constant fear of the ruler’s arbitrariness, and the self-obsessed ruler lives in fear of his subjects.

Plato’s views about a number of important matters would evolve over the course of his career. But not about this. He would return to this problem in his final dialogue, “The Laws,” to reaffirm and amplify his concern about pleonexia. There he condemns the wealthy as being incapable of virtue: “It is impossible that those who become very rich become also good.” Their very wealth betrays their character. To pursue great wealth is to abandon the legitimate moral concerns of others and to focus on one’s own selfish desires, since when one is consumed with pleonexia, there is room for little else.

As such, Plato reasons, the fabulously wealthy lack principles and a moral anchor outside of themselves. They feel no obligations to speak the truth or promote the common good, and no obligation to pay taxes or uphold contracts. To avoid these obligations, for such souls, is considered “smart.”

This is the Thrasymachian worldview. In choosing a president, Americans are now confronted with either embracing a Thrasymachus for our times or rejecting him.

David Lay Williams is professor of political science and Wicklander Fellow at DePaul University. He is author of “Rousseau’s Platonic Enlightenment” and “Rousseau’s Social Contract: An Introduction.” He is presently writing “The Greatest of All Plagues: Economic Inequality in Western Political Thought,” under contract with Princeton University Press.