Yet by implying that inflation needs to be monitored, she also implied that the government shouldn’t borrow and spend excessively, with which I heartily agree.

Furthermore, she was right to say that, in some cases, Americans overreact to government deficits. In fact, there is a long history of disputes by accountants on how deficits should be defined. For example, it has been proposed that the federal government should adopt separate capital and operating budgets — differentiating long-term investments from operating costs.

But it is not obvious how to do this, and the change has not been made. These accounting issues are technical and don’t provide useful slogans for influencing public opinion, as modern monetary theory does.

Representative Alexandria Ocasio-Cortez of New York may be the theory’s most visible supporter. In her advocacy of the Green New Deal program that she introduced with a fellow Democrat, Senator Edward J. Markey of Massachusetts, she has used the theory to dismiss criticisms that increased spending would require increased taxation.

Yet the Green New Deal — which the Republican-controlled Senate rejected on Tuesday in a procedural vote — looks awfully expensive. When the cost of her plan was pointed out to her in a National Public Radio interview with Steve Inskeep last month, Ms. Ocasio-Cortez said: “I think the first thing that we need to do is kind of break the mistaken idea that taxes pay for a hundred percent of government expenditure.”

When pressed, however, she said,“When we decide to go into the realm of deficit spending, we have to do so responsibly.” Because there are great opportunities for government investment at the moment and interest rates are low, these programs should go forward with deficit spending. Once again, this is a conventional argument: It makes sense to spend when the return on government investments exceeds the borrowing rate.

These are reasonable ideas. They are not always expressed in ways that are appealing to mainstream economists, however, so it’s not surprising that two Harvard economists recently wrote articles severely criticizing modern monetary theory. Kenneth Rogoff did so in “Modern Monetary Nonsense,” while Lawrence Summers wrote, “The Left’s Embrace of Modern Monetary Theory Is a Recipe for Disaster.”