No reasonable person can doubt that the US must eventually raise taxes. The country is running an unsustainable budget deficit. Its tax take, measured as a share of gross domestic product, is the lowest in the OECD. The 1990s suggest the US can raise revenues without damaging growth. Other countries have also managed similar feats. Sweden, for example, which collects 53 per cent of GDP in taxes, has grown faster over the past decade than the US, which collects 32 per cent, counting state and local government. From all this it follows that a distressingly large slice of the Republican party is unreasonable.

Equally, no reasonable person can doubt that the tax system must be used to soften inequality. Some inequality is good: it is a spur to enterprise and effort. But too much is clearly bad: it punctures meritocracy. As gaps in wealth and income have widened, it has become steadily harder for talented poor kids to compete against lavishly tutored rich kids armed with iPhones full of contacts. This is politically corrosive, morally unjust, and a shocking waste of human capital.

All this suggests Barack Obama is right to call for a “Buffett tax”. Yet in doing so, the president reminds us of why he is a disappointment.