Unlike Europe, America wasn’t bogged down by the legacy of feudalism, nor did it have a hereditary aristocracy. Noah Webster, best known for his dictionary, commented that there were “small inequalities of property,” a fact that distinguished America from Europe and the rest of the world. Equality of property, he believed, was crucial for sustaining a republic. During the Constitutional Convention, South Carolinan Charles Pinckney said America had “a greater equality than is to be found among the people of any other country.” As long as the new nation could expand west, he thought, it would be possible to have a citizenry of independent yeoman farmers. In a community with economic equality, there was simply no need for constitutional structures to manage the clash between the wealthy and everyone else.

The problem, of course, is that economic inequality has been on the rise for at least the last generation. In 1976 the richest 1 percent of Americans took home about 8.5 percent of our national income. Today they take home more than 20 percent. In major sectors of the economy — banking, airlines, agriculture, pharmaceuticals, telecommunications — economic power is increasingly concentrated in a small number of companies.

While much of the debate has been on the moral or economic consequences of economic inequality, the more fundamental problem is that our constitutional system might not survive in an unequal economy. Campaign contributions, lobbying, the revolving door of industry insiders working in government, interest group influence over regulators and even think tanks — all of these features of our current political system skew policy making to favor the wealthy and entrenched economic interests. “The rich will strive to establish their dominion and enslave the rest,” Gouverneur Morris observed in 1787. “They always did. They always will.” An oligarchy — not a republic — is the inevitable result.

As a republic descends into an oligarchy, the people revolt. Populist revolts are rarely anarchic; they require leadership. Morris predicted that the rich would take advantage of the people’s “passions” and “make these the instruments for oppressing them.” The future Broadway sensation Alexander Hamilton put it more clearly: “Of those men who have overturned the liberties of republics, the greatest number have begun their career by paying an obsequious court to the people: commencing demagogues, and ending tyrants.”

Starting more than a century ago, amid the first Gilded Age, Americans confronted rising inequality, rapid industrial change, a communications and transportation revolution and the emergence of monopolies. Populists and progressives responded by pushing for reforms that would tame the great concentrations of wealth and power that were corrupting government.

On the economic side, they invented antitrust laws and public utilities regulation, established an income tax, and fought for minimum wages. On the political side, they passed campaign finance regulations and amended the Constitution so the people would get to elect senators directly. They did these things because they knew that our republican form of government could not survive in an economically unequal society. As Theodore Roosevelt wrote, “There can be no real political democracy unless there is something approaching an economic democracy.”

For all its resilience and longevity, our Constitution doesn’t have structural checks built into it to prevent oligarchy or populist demagogues. It was written on the assumption that America would remain relatively equal economically. Even the father of the Constitution understood this. Toward the end of his life, Madison worried that the number of Americans who had only the “bare necessities of life” would one day increase. When it did, he concluded, the institutions and laws of the country would need to be adapted, and that task would require “all the wisdom of the wisest patriots.”

With economic inequality rising and the middle class collapsing, the deep question we must ask today is whether our generation has wise patriots who, like the progressives a century ago, will adapt the institutions and laws of our country — and save our republic.