They fall into two main categories. The first is who benefits from the tax plan. “Wealthy Americans are not getting a tax cut,” Cohn said on “Good Morning America.” He was echoing a promise that Mnuchin had made before the inauguration: “Any reductions we have in upper-income taxes will be offset by less deductions, so that there will be no absolute tax cut for the upper class.”

No one needs to read a sophisticated analysis (although you can do that, as well) to know these claims are ridiculous. Trump’s tax plan is reducing the top income-tax rate to 35 percent, from 39.6 percent. It is deeply cutting corporate taxes, which benefits people who own a lot of stock. It is eliminating the estate tax.

Want to guess how many families in New York State — population 20 million — are wealthy enough that they’re likely to pay any estate tax next year, according to an estimate based on I.R.S. data? Just 470. The number is so low in Montana, Vermont, West Virginia and four other states — likely fewer than 10 families in each — that the I.R.S. doesn’t provide details, to avoid privacy concerns.

There is no way to make up for tax cuts this large by eliminating deductions, as Mnuchin claimed. The administration isn’t trying very hard, anyway. The deductions for charitable donations and mortgage interest, including on second homes, will remain.

Then there are the two men’s deficit claims. “This tax plan will cut down the deficits by a trillion dollars,” Mnuchin said. Cohn claimed that “we can pay for the entire tax cut through growth.” These may seem marginally more defensible, because they’re predictions. But they’re silly predictions, not so different from my vowing to lose weight by eating more ice cream.

The Harvard economist Greg Mankiw coined the phrase “charlatans and cranks” specifically to describe people who claim that tax cuts pay for themselves. And Mankiw is a conservative who’s worked for George W. Bush and Mitt Romney.