What a difference an assumption can make. Since the Industrial Revolution in the second half of the 18th century, a fortunate fraction of mankind has basked in a world of plenty. Living standards have risen exponentially as vast numbers of people escaped the dire poverty that had been the lot of their forebears for ages untold. The share of income spent on food in these revolutionized parts of the globe has fallen dramatically—in many industrialized countries to below 10 percent, and as low as 7.4 percent in the United States (as of 2006).

For most of the past two centuries, the denizens of plenty have assumed that the break with bleak pre-industrial poverty was a permanent one. They have often assumed, as well, that the ways of plenty would eventually spread to encompass the entire human family, and that when they did, most of the ancient misanthropies that have afflicted humankind would vanish from the face of the earth. The end of scarcity, it has been widely believed, would end the causes for greed and envy, avarice and war. War would no longer be “worth it”, a presumption, it is fair to say, that lies at the very plinth of the Whig interpretation of history.

This is by now an old idea, but it is a sturdy one that has been propelled forward by the end of the Cold War and the cluster of phenomena known by the catchall phrase “globalization.” Indeed, new and improved versions of the Whig interpretation have gained much credence since Herbert Butterfield coined the term in 1931. Thanks to globalization and the parallel spread of the received macroeconomic gospel, many millions more have been raised from dire poverty in the past two decades—a feat no amount of foreign aid could ever have produced. This unarguable achievement, many have claimed, could portend the end of poverty in our times. Add the comforting lyrical harmonies of democratic peace theory to the benign chorus of globalization and one gets a world veritably transformed very much for the better—perhaps even “the end of tyranny”, as George W. Bush put it in his second Inaugural Address.

What if, however, the foundational assumption is wrong? What if the past two centuries, particularly the past two decades, have been not a reflection of the new rules of earthly progress, but exceptions to the old rules that once were and again shall be? In other words, what if Thomas Malthus turns out to have been right after all, and Adam Smith wrong?

For most of the past two centuries, few would have acknowledged even the possibility of such a thing coming to pass. Malthus was dubbed an intellectual fossil,...