Mr. Mosler’s ideas, which go under the label of “modern monetary theory,” or M.M.T., are clearly on the fringe, drawing skeptical reactions even from many liberal Keynesian economists who agree with some of his arguments. But they have attracted a growing following, flourishing on the Internet and in a handful of academic outposts, as he and others who share his thinking have made the case that austerity budgeting in the United States and in Europe is doing irreparable harm.

Like many Keynesian economists, Mr. Mosler and other modern monetary theorists are particularly disturbed by the longstanding campaign articulated and financed by Peter G. Peterson, a former commerce secretary who co-founded the Blackstone Group private equity fund, to reduce the deficit or else.

“There’s a whole deficit lobby of Peterson-funded groups arguing we’re turning into Greece,” said James K. Galbraith, an economist at the University of Texas at Austin. “They’re blowing smoke and the M.M.T. group has patiently explained why.”

Still, even for those with some knowledge of economics, the tenets of the modern monetary theory can make your head spin. The government does not tax its citizens to pay for federal spending. It taxes them to ensure they use the dollar and to help to regulate demand. Since the government prints the dollar, it can never run out of money and it need never balance its budget, not even to prevent the crowding out of private investment when the economy is humming along.

What about inflation? “What about it?” Mr. Mosler replied. “How can the United States have $16 trillion in debt and still be on the verge of deflation, even when Chairman Bernanke’s using every alphabet-soup trick in his book?”

To mainstream economists, Mr. Mosler and his adherents represent something of a counterpoint to the handful of academics on the right who believe the United States should return to the gold standard because the government is supposedly going bankrupt and the Federal Reserve under Ben S. Bernanke is debasing the currency.

“They deny the fact that the government use of real resources can drive the real interest rate up,” said Mark Thoma, an economics professor and widely followed blogger who teaches at the University of Oregon. After delving into the technical details of modern monetary theory for a few minutes, he paused, then added, “I think it’s just nuts.”

But just as a return to the gold standard has attracted a popular following — including many supporters of Ron Paul, the charismatic former Texas congressman — so has modern monetary theory, which has been spread on the great stage of the Web. A thriving academic blogosphere brings ideas up and knocks them down, and popular sites like Business Insider and Naked Capitalism have given modern monetary theorists a platform to join in.

“These ideas definitely aren’t disseminated through published academic journals,” said Stephanie Kelton, an economist at University of Missouri-Kansas City, [more recently She served as Chief Economist on the U.S. Senate Budget Committee (minority staff) in 2015 and then became an Economic Advisor to the Bernie Sanders 2016 presidential campaign.] who coined the term “deficit owls” to distinguish modern monetary theorists from “deficit hawks.” “It’s all on the Internet.”

Mr. Mosler has played a pivotal role in promoting the theory, and unlike many economists he has the resources to do so. He runs a popular blog called the Center of the Universe, a sly joke, perhaps, given that tiny, tropical St. Croix, which is about 1,200 miles from Miami, is the easternmost point in the United States. He eagerly appears on radio programs and on television. Recently, he went on a tour of Italy to promote his anti-austerity ideas.

He has also helped to build an infrastructure to mint new modern monetary theorists, helping to found the Center for Full Employment and Price Stability at the University of Missouri-Kansas City, and financing a small army of graduate students. “Someone once said that economics advances one funeral at a time,” Mr. Mosler said, chuckling. “The hope is that we have a generation of economists coming up who really understand how things work and can put those ideas to a public purpose.”

[… abridged …]

Mr. Mosler started his career at a small bank in Connecticut, and eventually became a Wall Street trader. It was there, he said, that he developed an intuitive understanding of how the economy works — one very different from that of policy makers in Washington and the vast bulk of academics.

“All debt management is, is debiting and crediting different accounts,” Mr. Mosler said, recalling seeing numbers appear and disappear from his computer at Bankers Trust in New York in the 1970s. “Can the federal government run out of dollars? No, because the Fed could pipe in a bigger number. That number doesn’t come from anywhere. It’s like when a player scores a field goal at a stadium. Three points just appear. The government is just the scorekeeper for the dollar.”

In the early 1980s, he left Wall Street and along with a partner, Clifford Viner, who is now the owner of the Florida Panthers hockey team, founded a hedge fund in Boca Raton, Fla. The fund made relatively few, relatively complicated financial bets, said Michael Reger, a partner of Mr. Mosler’s for the last 20 years. “He’s an urban myth,” Mr. Reger said of the affable, talkative and bookish Mr. Mosler.

Mr. Mosler’s fund has made a number of bets informed by his theory. For instance, Mr. Reger said, when the Treasury was paying down the United States debt during the Clinton years, many bond traders thought that prices would spike because of increasing scarcity. But Mr. Mosler predicted that no such scarcity would ever materialize, and shorted the bonds.

That trade panned out, though others have not. The business lost hundreds of millions of dollars betting that Russia would not default on its debts. That country’s fixed exchange rate spurred it to go belly up, Mr. Mosler said.

[… abridged …]

… entering retirement, Mr. Mosler has more than enough work to do promoting his monetary theories, he said.

“Economics is about the allocation of scarce resources,” Mr. Mosler said. “If there’s a food shortage, you have a real problem in divvying up the food. Right now, we have a dollar shortage because of mistaken notions about how the monetary system works. How does that make any sense?”