If your image of the typical rich person is someone who collects interest and dividend checks and spends long afternoons relaxing on his yacht, you are decades out of date. The leisure class has been replaced by the working rich.

Another piece of the puzzle is that Mr. Buffett’s tax burden is larger than it first appears, because he is a major shareholder in Berkshire Hathaway.

When the C.B.O. studies the tax burden, it includes all federal taxes, including individual income taxes, payroll taxes and corporate income taxes. In its analysis, payroll taxes are borne by workers, and corporate taxes by the owners of capital. For the richest 1 percent of the population, 9.3 percentage points of their 31.1 percent tax rate comes from the taxes that corporations have paid on their behalf. The corporate tax would undoubtedly loom large if the C.B.O. were to calculate Mr. Buffett’s effective tax rate.

None of these calculations, however, say whether the rich are paying their fair share. Fairness is not an economic concept. If you want to talk fairness, you have to leave the department of economics and head over to philosophy.

The quintessential political philosopher of modern liberalism is John Rawls, the author of the 1971 classic “A Theory of Justice.” Professor Rawls concluded that the primary goal of public policy should be to redistribute resources to help those at the very bottom of the economic ladder. If Professor Rawls were alive today, he would most likely want to raise the top income tax rate of 35 percent in order to finance a more generous safety net. And for much the same reason, he would probably raise taxes on the middle class as well.

Professor Rawls would get a vigorous debate from his Harvard colleague, the libertarian philosopher Robert Nozick. In his 1974 book, “Anarchy, State, and Utopia,” Professor Nozick wrote: “We are not in the position of children who have been given portions of pie by someone who now makes last-minute adjustments to rectify careless cutting. There is no central distribution, no person or group entitled to control all the resources, jointly deciding how they are to be doled out. What each person gets, he gets from others who give to him in exchange for something, or as a gift. In a free society, diverse persons control different resources, and new holdings arise out of the voluntary exchanges and actions of persons.”

To libertarians like Professor Nozick, requiring the rich to pay more just because they are rich is little more than officially sanctioned theft.