Racial difference is a constant, even unremarkable presence in city life — as simple as the way that, as you walk from one neighborhood to another, you’re aware of whether or not you “belong.” Racial differences, though, aren’t always cause for wariness or unease. Often, they’re invigorating. In The Cosmopolitan Canopy: Race and Civility in Everyday Life, the Yale sociologist Elijah Anderson writes about those parts of the American city that allow “complete strangers to observe and appreciate one another” across racial barriers. Anderson calls these spaces “cosmopolitan canopies,” and says they let ordinary people become amateur anthropologists, watching and, eventually, reaching out to people of whom they’d be more wary in other places. His broader question: can we encourage the growth of cosmopolitan canopies? Or do they only grow from the bottom up?

President Obama in Philadelphia’s Reading Terminal Market.

Anderson’s book is focused on Philadelphia, and starts with a walking tour of that city from a racial point of view: he takes in the Philadelphia equivalents of Back Bay, Downtown Crossing, Faneuil Hall, and South Station. Walking through Philly’s neighborhoods, Anderson writes, often means having “a pervasive wariness towards strangers,” created by the feeling that each neighborhood “belongs” to one group or another. By and large, this proprietary feeling is the rule. But scattered throughout the city there are oases of cosmopolitanism — places characterized by “acceptance of the space as belonging to all kinds of people.”

In fact, in such places cosmopolitanism is part of what draws a crowd: people enjoy meeting and watching other people who are different from themselves. Anderson looks in detail at Philadelphia’s Reading Terminal, a huge, enclosed food court, shopping area, and grocery market where “no one group claims priority.” At Reading Terminal, Amish farmers mingle with white, Asian, Hispanic, and African-American shopkeepers, restauranteurs, and customers — in fact, everyone’s smooshed together and forced to interact by the crowds. There’s a pervasive atmosphere of trust, openness, and curiosity, and, in interviews with Reading regulars, Anderson finds that many people very consciously approach the Market as a place where they can be racially open. They enjoy “watching the show” put on by the diverse crowd, and enjoy experimenting with a more open kind of social life: trying strange food, striking up casual conversations with different kinds of people, and playing a part in a self-consciously open society. This isn’t about self-congratulation — it’s about a relaxation of the emotionally costly social guardedness that one must uphold the rest of the time.

Why do cosmopolitan canopies like Reading Terminal work? (Anderson points to many others: parks, transportation hubs, sports stadiums, even the Whole Foods.) These are safe spaces, separate from the street, made warm and intimate by a shared experience — food, shopping, travel, cheering on a team. But there’s also an intangible ingredient: a mood, Anderson writes, of “civility” that allows people “to stretch themselves mentally, emotionally, and socially,” and to develop “the growing social sophistication that allows diverse urban people to get along.” Because they’re so hard to replicate, Anderson argues, they ought to be treasured and protected — and those of us who enjoy them ought to treat them “not as ‘time out’ from normal life but as a model for what social relationships could become.” That’s how cosmopolitanism spreads.