In Plato’s Republic, Socrates describes an ideal city-state, where material necessities are satisfied and a just society is achieved. The sage loosens his toga and spins a fantasy of citizens relaxing on their pallets, feasting on loaves of plain barley and wheat, enjoying ordinary wine. Bedecked in garlands, their children gamboling about them, they praise the gods who have bestowed such good fortune. They do not abandon good sense, however, do not run up their credit cards or purchase fancy watches. Exemplars of the rational Homo economicus that a modern utilitarian economist would recognize, “they take care that their families do not exceed their means,” says Socrates.

Not so fast, the student Glaucon pipes up. What the teacher is talking about is a base society, in which people eat just to fill their stomachs—a “City of Pigs.” But people do not want to live like pigs. If they have enough, they will want more. “People who are to be comfortable are accustomed to lie on sofas, and dine off tables, and they should have sauces and sweets in the modern style.”

What makes us want luxury goods? Taste? Pathology—luxury fever, affluenza? Advertising (that is, gullibility)? All of the above? Glaucon doesn’t even ask the question. He is talking about desire itself, observing—as others from Proust to the Rolling Stones have—that desire is rarely satisfied by satisfaction. Possession affords a flicker of warmth, which almost inevitably cools. Once we get what we want, we want something else, something different, better, something less attainable. The more pressing the desire, the harder it is to distinguish from need. Luxury may be defined not so much by the cost or usefulness of the commodity but by the ratio of its desirability to its attainability.

Capitalism needs us to want what we do not have.

Glaucon understood, as Paul Bloom does, that goods are inextricable from human life. In today’s consumer society, goods and purchased experiences are even more critical to everything we do, feel, and are. Through them we communicate our identities, interact with friends, conduct international politics. “Consumption is the very arena in which culture is fought over and licked into shape,” sociologist Mary Douglas and economist Baron Isherwood write in The World of Goods (1979). “Take [goods] out of human intercourse and you have dismantled the whole thing.”

Whether from Kmart or Cartier, goods are not intrinsically moral or immoral, practical or trivial. In the 1960s, for instance, an ethic of anti-consumerism coexisted with the purchase of records, motorcycles, and hallucinogens, which could abet liberation or even express rebellion. “The pleasure we get from luxury goods,” Bloom says, “is psychologically on par with other, more respected wants.” I would go further: pleasure is a human need, and goods are a primary supplier of pleasure.

But that pleasure is not unproblematic, as Socrates, in the fourth century, B.C., illuminated.

In Plato’s telling, the teacher listens to Glaucon’s critique and carries it to its logical end. People will want not just sofas and tables, Socrates reasons, but “also dainties, and perfumes, and incense, and courtesans, and cakes, all these not of one sort only, but in every variety.”

To make the fancy furniture and decorate the beautiful rooms, embroiderers and painters will have to be employed, and gold and ivory procured. These needs will in turn necessitate the conquest of more territory, as well as the protection of the state from its equally voracious neighbors. The taste for sauces and sweets leads to imperial ambitions, in other words, and empire necessitates war.

Plato suggests that the tide of expectations rises as surely as the moon pulls the sea. Yet the philosopher of balance believed that a surfeit of personal desire was the enemy of social harmony. Twenty-five centuries later, when Chinese peons make Americans’ iPhones, and Europe’s car exhaust parches Africa’s farmlands, Marxists, tree-huggers, and popes—Bloom’s utilitarians and moralists—tell versions of Socrates’s narrative.

We are left with a conundrum. Our pleasures reside in things; our economy is fueled by desire, ignited and fanned by advertising and easy credit. Yet the satisfaction of our desire by the relentless production and marketing of goods is depleting the earth of its air and its animals and putting some of the world’s people under others’ boots. We have enough stuff; most Americans have more than enough. Yet capitalism needs us to want what we do not have, and desire for what we do not have is an infinitely renewable resource.