The hitch, as Caplan points out, is that this miracle of aggregation works only if the errors are random. When that’s the case, the thousands of ill-informed votes in favor of the bad health plan are canceled out by thousands of equally ignorant votes in favor of the good plan. But Caplan argues that in the real world, voters make systematic mistakes about economic policy — and probably other policy issues too.

Caplan’s own evidence for the systematic folly of voters comes from a 1996 survey comparing the views of Ph.D. economists and the general public. To the exasperation of the libertarian-minded Caplan, most Americans do not think like economists. They are biased against free markets and against trade with foreigners. Absurdly, they think that the American economy is being hurt by too much spending on foreign aid; they also exaggerate the potential economic harms of immigration. In a similar vein, Scott L. Althaus, a University of Illinois political scientist, finds that if the public were better informed, it would overcome its ingrained biases and make different political decisions. According to his studies, such a public would be more progressive on social issues like abortion and gay rights, more ideologically conservative in preferring markets to government intervention and less isolationist but more dovish in foreign policy.

If the public doesn’t know how to think, is there a solution? Caplan has some radical medicine in mind. To encourage greater economic literacy, he suggests tests of voter competence, or “giving extra votes to individuals or groups with greater economic literacy.” Until 1949, he points out, Britain gave extra votes to some business owners and graduates of elite universities. (Since worse-educated citizens are less likely to vote, Caplan dislikes efforts to increase voter turnout.) Most provocatively, perhaps, in an online essay Caplan has suggested a curious twist on the tradition of judicial review: If the Supreme Court can strike down laws as unconstitutional, why shouldn’t the Council of Economic Advisers be able to strike down laws as “uneconomical”? (Caplan’s book has been warmly recommended by N. Gregory Mankiw, the former chairman of President Bush’s Council of Economic Advisers, although Mankiw did not allude to this particular proposal.) Caplan also suggests changing the educational curriculum to stamp out biased beliefs in voters and policy makers alike — a suggestion as old as Plato’s wish that a city’s ruling guardians be schooled in the “royal science” of governance, which has seemingly been reincarnated as economics.

Caplan’s argument has kicked off some stormy Internet debates. The liberal blogger Ezra Klein wrote: “Obviously I, like most coastal-bred elitists, don’t think voters make terribly good decisions. But I also don’t think economic actors are particularly rational.” He might have added that many policy issues cannot be decided on the basis of avowedly rational expert judgment alone. Take immigration, where governments weigh not just economic costs and benefits but also demands of national identity and cosmopolitanism. Or war: it’s very complicated, so should we abandon military planning to the professional generals?

Caplan’s view of democracy is all about efficiency, not legitimacy. But some time ago, the political scientist Samuel P. Huntington pointed out the weakness of dictatorships that justify their rule by only the quality of their job performance: as soon as something goes wrong — a war is lost or inflation skyrockets — the public has no further reason to put up with a despot. If the public asked Caplan’s Council of Economic Advisers by what authority it struck down a law, the council members could point only to their diplomas and peer-reviewed articles. A democratic public may not always like — or understand — the government’s policy, but the consent of the governed gives the citizens a reason not to reject the whole system.