ANCIENT Greek and Roman politics rested on a conundrum. Lest they undermine social peace, the poor could not routinely threaten the lives or property of the rich. But unless the laws were fair enough to the poor, why should the plebs respect them?

Greeks and Romans addressed this challenge — one that we continue to face — with three distinct models. Athenian democracy empowered the poor, while employing the rich to serve; Roman republicanism empowered the rich, while building in special protections for the poor; and the political theory of Aristotle imagined a new politics of what he called the “middling” class.

In full flower in the fifth century B.C., the Athenian democracy enfranchised all male citizens without requiring any wealth qualification (though slaves were excluded from political participation altogether). This created a majority who were poor — “the many,” as opposed to a small elite, “the few.” Who were the many? By some reckonings, they were 90 to 95 percent of adult citizens, all those who had to work for a living; by others, they were the two-thirds who lacked the means to qualify for elite military status.

As an anonymous writer at the time observed, the poor majority perfected a way of wielding its power by making use of the power of the rich. On one hand, the poor often elected the wealthy to key offices and followed their advice in the assembly; on the other hand, they used their collective power in the assembly, juries and executive council to restrain the wealthy and rein in corruption. And so the poor majority asserted ultimate control over the elites, even while allowing them considerable influence.

The Roman poor fought more of a rear-guard action. Roman republican politics expected the rich to hold sway in the offices and also in the Senate. Technically, the popular assemblies dominated by the poor majority had the sole power to approve all laws. Yet in other kinds of assembly, citizens voted by property class, starting with the richest groups, who sometimes decided the issue before the poorer groups got to cast their votes.

The balance between rich and poor in Rome was unstable. In 494 B.C., for example, the poor were so burdened by debts that they effectively went on strike: They put down the tools of their labor and absented themselves from the spaces under elite control. By seceding from the city, they forced the establishment of a new political institution: tribunes, whom the plebs would elect to defend their interests. Among their powers, the tribunes could veto proposed senatorial measures and provide a safe haven for those who were threatened or abused by members of the elite in the markets or on the streets.

Today, this model might inspire giving a panel of “lottery-selected, nonwealthy citizens” a set of powers to intervene in and check federal proceedings, as the political theorist John P. McCormick has proposed. As Roman tribunes had the power to veto Senate decisions, so modern tribunes could have the power to cast a certain number of legislative vetoes each year. Another kind of modern tribune would be ombudsmen to whom the poor could appeal against routine bureaucratic indignities, as the Roman poor were protected by a tribune’s “sacrosanct” physical presence.

What if we were to abandon Athenian and Roman models of managing class conflict, in favor of a promised land in which virtually everyone was middle class? That model has an ancient pedigree too, but, tellingly, it is found only in philosophy, not in Greek or Roman history. In his “Politics,” Aristotle imagined what he called a “middling” regime that would cultivate and expand a group of citizens who were neither rich nor poor, instead being “equals and similar,” and make them the political center of gravity.

Middling dominance would require making it impossible for the rich to use their money to buy special political power. At the same time, it would marginalize the poor, who would no longer make up a numerical majority. The philosopher called this “middling” model “the best constitution for most states and the best life for most men,” even though his highest ideal was a regime in which all citizens would be leisured, relying on noncitizen artisans, farmers and slaves to do the dirty work.

Yet a modern regime based on this Aristotelian “middling” model would be less congenial to both left and right than either might imagine. It would have to tax the rich drastically in order to reduce their social and political power, while at the same time reining in support for the poor, in order to keep the balance squarely away from each extreme. In the end, the Aristotelian “middling” model is no less a recipe for class dominance than the Athenian or Roman regimes, and it, too, would most likely require the services of a permanent underclass.

This range of ancient options suggests that it is pointless to imagine a politics in which no class is dominant or one in which the interests of different classes don’t sometimes conflict. History and philosophy alike counsel that the most practical course is to moderate class conflict, not by pretending it away, but through the self-assertion of the weaker classes and institutionalized recognition of their interests.