Some of this confusion is deliberate. By pushing for less government, regardless of the situation, contemporary libertarians act as a kind of lobbyist working on behalf of the affluent. Less government tends to mean lower taxes for the people with the most money to lose to taxes. Less government also means cuts to schools, and health-insurance and retirement programs on which the affluent do not depend.

But not all of the analytical errors of libertarianism are so cynical. Some stem from the honest intellectual mistake of confusing a good idea with the good idea. Because Rodrik’s focus is economics, he frames this mistake in terms of theoretical models, which are a central tool of both social science and natural science. Rodrik compares them, somewhat impishly, to fables, but he means the comparison as a compliment to both.

“What are economic models?” he asks. “The easiest way to understand them is as simplifications designed to show how specific mechanisms work by isolating them from other, confounding effects. A model focuses on particular causes and seeks to show how they work their effects through the system.” A fable, similarly, trades complexity and comprehensiveness for a clear but still true lesson.

The trouble comes when economists — and the rest of us — try to make such a lesson universal. Universality has its place in the physical sciences but rarely in the social sciences. “We cannot look to economics for universal explanations or prescriptions that apply regardless of context,” Rodrik writes. “The possibilities of social life are too diverse to be squeezed into unique frameworks.”

The lure of universality is not a uniquely right-wing phenomenon, of course. The left and center suffer from it, too. Liberals, for instance, can slip from believing that government is often necessary into believing that it is inherently effective — and defend public schools and anti-poverty programs that ill serve the poor. Centrists sometimes leap from the reasonable judgment that neither political party has a monopoly on the truth to the unreasonable one that the truth on any one issue lies roughly halfway between the extremes.

That last point has a particular relevance to modern American politics, and to the problems Ebenstein describes. While all political ideologies (not to mention all human beings) are susceptible to overlearning a lesson, the damages from that mistake come mostly from the right half of the spectrum in the United States today. The political right has spent five years wrongly predicting hyperinflation and, in the process, kept the federal government from doing more to combat unemployment. There are similar stories about climate policy, tax policy, health care and even voting rights and voter fraud.

Reducing complex issues to their essence is unavoidable. The alternative is an often paralyzing level of detail. Rodrik cites a story by the Argentine writer Jorge Luis Borges, “On Exactitude in Science,” about a mythical empire in which the mapmakers could not tolerate any oversimplification. Ultimately, they created a map as large as the empire itself, which is no more useful than a map consisting of a single tiny dot — or an economic philosophy that offers only one answer, no matter the question. As Rodrik says, quoting an adage often attributed to Einstein, “Everything should be made as simple as possible, but no simpler.”