Debate persists about which demographic mix best drives a city’s success.
Late one afternoon nearly two decades ago, having made my way down the length of Manhattan’s west side, I met my grandfather at a quaint Italian restaurant in the West Village. He greeted me in the vestibule, gave me a hug, and asked how I’d thought to recommend this particular trattoria. I explained that an old buddy who’d grown up in New York had suggested it, but I quickly added that in the near future neither of us would have to depend on personal recommendations. That same friend had recently offered me a demonstration of Vindigo (a precursor to Yelp, the social networking site that rates local businesses). Once installed on a Palm Pilot (a precursor to the iPhone), the app would list all the restaurants near any given Manhattan intersection, sorted by cuisine. After a user selected the restaurant, Vindigo would offer walking directions.
I’d expected my grandfather to guffaw—oh, the wonders of modern technology! Instead, he frowned. “Marc, when I was a young salesman traveling between hosiery mills in the small towns of North Carolina, I’d get off a train with nothing but a suitcase and make my way over to a friendly looking stranger. ‘Is there a good place to eat around here?’ More often than not, that guy would direct me to a hole in the wall or a diner a few blocks away. With some frequency, we’d strike up a conversation—sometimes he would join me for the meal. He’d tell me when he served in the war and share some of the local folklore. After a few minutes we’d invariably be talking about our families. That’s how I got to understand the world—by talking to strangers. If I returned the next year, I’d often look up the same fellow. With all these fancy technologies you’re telling me about, how are people going to get to know one another? You ask me, I think it’s going to make everyone lonely.”
I listened respectfully to my grandfather, not entirely surprised to discover that he was a Luddite, but I dismissed his criticism all the same. A handful of introductory-level college courses had convinced me that technology always disrupts existing patterns of behavior—and that the naysayers generally are proved to be naive. So my grandfather and I ordered our pasta, the conversation turned to lighter topics, and I relegated his ornery objection to the back of my mind. Only years later, after more than a decade of work in politics and government, did I begin to wonder whether he hadn’t been on to something. Maybe the disruptive changes that define contemporary life have, in fact, altered social patterns in ways many of us fail to appreciate.
The Rise and Fall of Urban Neighborhoods
Roughly a century ago, the eminent thinker and social critic Lewis Mumford argued that the United States had, to that point, endured three major migrations. The first extended the nation westward, across the Appalachians and eventually to the Pacific. The second relocated a pastoral and agrarian population to small factory towns. The third migration, which began around of the turn of the twentieth century, fueled the growth of great urban metropolises, places defined by enormous manufacturing plants and tenements teeming with immigrants.
At that time, much of well-to-do America was worried that cities would prove the nation’s undoing. “Chicago School” sociologists, then part of what was only a nascent academic discipline, feared the spread of what many termed “anomie.” They worried that those raised in urban squalor would emerge a different breed from those reared in the purportedly wholesome rural and small-town environments of nineteenth-century America. In 1938, Chicago School member Louis Wirth rendered a formal diagnosis:
The distinctive features of the urban mode of life have often been described sociologically as consisting of the substitution of secondary for primary contacts, the weakening of bonds of kinship, and the declining social significance of the family, the disappearance of the neighborhood, and the undermining of the traditional basis of social solidarity…. Personal disorganization, mental breakdown, suicide, delinquency, crime, corruption, and disorder might be expected under these circumstances to be more prevalent in the urban than in the rural community. This has been confirmed in so far as comparable indexes are available.11xLouis Wirth, “Urbanism as a Way of Life,” in The City Reader, ed. Richard T. LeGates and Frederic Stout (London, England: Routledge, 1996), 195–96. First published 1938.
Reacting to such concerns, contemporary reformers rushed to established a range of institutions designed to pull society from the brink of dissolution. Settlement houses proved one of the more benign examples. More malign was Prohibition, a law that, by some measures, was aimed less at proscribing alcohol consumption than forcing recently arrived Irish, German, Italian, and Jewish immigrants—many of them living in cities—to accommodate to the moral pretenses of a more culturally conservative society than the ones these new arrivals had left behind. Beneath the rush to weave them into the fabric of traditional society was a fear that those who failed to find a niche might revolt in support of anarchy. Sacco and Vanzetti weren’t tried and executed in a vacuum.
Fortunately, urban America did not devolve into the den of iniquity and decay many had originally feared. What haughty outsiders perceived as tracts of endless blight were actually understood by their occupants to be a collection of coherent neighborhoods. Residents felt connected to the people living nearby. City dwellers in each collection of blocks tended to send their children to the same schools, shop in the same marketplaces, worship in the same churches or synagogues, and work in the same sweatshops and on the same factory floors. In other words, urban America was organized in much the same way as pastoral America—just in tighter quarters.
Today, more than a century after Americans began pouring into industrial metropolises, we’ve lost track of the remarkable continuity that spanned the three Mumfordian migrations. Like eighteenth-century colonial villages and nineteenth-century frontier towns, twentieth-century urban neighborhoods were defined by a very specific social architecture. Samuel Benninger, an English Congregationalist minister who visited America in the early 1800s, had noted “Whether Anglican or separatist, we [Englishmen] have a notion of Church and nation. In the American states, even Anglicans speak only of village and congregation.”22xSamuel Benninger, An Account of a Visitation to America: With Observations, Facts, and Conversations Recorded toward the Purpose of Truth (London, England: privately published, 1807), 43. Quoted in Gregory H. Singleton, “Protestant Voluntary Organizations and the Shaping of America,” American Quarterly, Vol. 27, No. 5, December 1975, 551, https://www.jstor.org/stable/pdf/2712440.pdf. Accessed March 29, 2017. And that same tradition—notable in contrast to European societies parsed according to class and confessional distinctions—frequently mapped onto newly arrived immigrant populations as well. Chicago School sociologists had been so disoriented by the apparent wretchedness of the urban landscape that they had assumed that the township-oriented building blocks of American society would disappear as well. But they were wrong.
How misguided were they? Today, by some measures, the urban neighborhoods of the early twentieth century have become the model for close-knit communities. Yes, they were strictly sorted by race and ethnicity. The poorer among them lacked proper sanitation; they were cesspools of disease and poverty. We should never fail to acknowledge the hardships of deprivation. But we should also acknowledge that, even in their tumult, many were vibrant, interactive, cohesive social units in and of themselves. One need only read The Lost City, Alan Ehrenhalt’s masterful 1995 portrayal of three divergent neighborhoods in and around Chicago—the white working-class parish of St. Nicholas of Tolentine; the mostly African American neighborhood of Bronzeville; and tonier, suburban Elmhurst—to understand how tightly bound these communities could be, even as they varied dramatically from one to the next. As Ehrenhalt put it, “These worlds of bungalow, tenement, and ranch house, different as they were, nonetheless had something important in common. They were clear geographical communities, and their inhabitants identified with them on that basis…. A neighborhood nearly everywhere in the 1950s was a tangible thing, a piece of ground, a physical marker in life…a place in which people lived their lives more or less in public, in full view of their neighbors.”33xAlan Ehrenhalt, The Lost City: Discovering the Forgotten Virtues of Community in the Chicago of the 1950s (New York, NY: Basic Books, 1995), 28–29.
The halcyon days of vibrant urban neighborhoods did not last forever. Beyond the desire to escape the cramped quarters of tenement neighborhoods, the fourth (predicted) migration in Mumford’s analysis was born of the automobile, the expressway, and the mortgage interest deduction. Throughout the twentieth century—and even, by some measures, into this one—Americans moved out of the cities and into the suburbs. Between 1950 and 1980, all but seven of the nation’s twenty-five largest cities saw their populations decline. And where did these erstwhile urbanites go? In his award-winning examination of suburban life, Crabgrass Frontier, historian Kenneth Jackson quotes columnist Erma Bombeck’s characterization of those “small, controlled communities where for the most part everyone has the same living standards, the same weeds, the same number of garbage cans, the same house plans, and the same level in the septic tanks.”44xKenneth T. Jackson, Crabgrass Frontier: The Suburbanization of the United States (New York, NY: Oxford University Press, 1985), 4.
No one can say for sure what might have happened had the federal government not subsidized the middle-class stampede to single-family homes. Maybe Americans with sufficient means to live in bedroom communities would have remained urban renters; maybe many would have converted leased buildings into co-ops and condos. Without the federal subsidies that made interstate highways possible, the commute to downtown might have been too long to endure. The tax base supporting high-quality public schools might have remained local. Whatever might have happened, what did happen was a travesty. For the most part, the city became the place Americans called home when they had few other places to go.
The growth of suburbia can’t be separated from a concomitant shift: the upheaval known broadly as “the Great Migration.” Between the early 1900s and 1970, roughly six million African Americans moved from the Jim Crow South to industrialized cities elsewhere, most frequently to metropolises like New York, Chicago, and Los Angeles. But while the new arrivals seemed to presage the rise of a new diversity in American cities, things took a very different course. As Princeton sociologist Doug Massey has argued, while the Great Migration spurred additional regional diversity, cities actually became more segregated on a neighborhood-by-neighborhood basis. “White flight” upended the previous perception of urban America. By the end of the twentieth century, cities were widely presumed to be poor, slum-filled, crime-riddled, and drug-infested.
Urban America Is Back
Nearly a fifth of the way through the twenty-first century, America’s understanding of the urban tableau has turned once again. In his most recent book, The Great Inversion, Alan Ehrenhalt argues that the twentieth century’s suburban migration has been overtaken by something new—namely, the return of prosperity and privilege to urban neighborhoods. America’s burden today, some argue, isn’t so much to buoy the poor people trapped in decaying metropolises—a frequent charge through so much of the twentieth century. Rather, the challenge is to deal with the rapid pace of “gentrification,” namely, the displacement of poorer communities by an influx of young, relatively affluent residents eager to reclaim the amenities offered exclusively in urban cores.
Within cities themselves, new wealth has been greeted with great fanfare—except by those who see gentrification as a threat to the communities that remained during the decades of white flight. Boosters cite a whole range of advantages. Among progressives, maybe no single feature is more important than the potential energy savings: The carbon emissions generated by large populations living in larger buildings and using mass transit is markedly less than what is thrown off by those living in freestanding suburban homes who commute to and from work in cars. As Harvard economist Edward Glaeser observed in his 2011 book Triumph of the City, the public health benefits of a more ambulatory lifestyle constitute an additional advantage of urban living.
But not everyone has been so thrilled with the sea change. Though no single factor can explain Donald Trump’s victory in the 2016 election, the academically credentialed, socially progressive millennials streaming to Boston, New York, and Palo Alto may be more culturally at odds with other parts of the country than some realize. The concept of “disruption” is celebrated in Silicon Valley—indeed, it’s the defining consequence of successful technological innovations. But for many of those living in other parts of the country—in suburban or exurban locales such as Michigan’s Macomb County, Pennsylvania’s Luzerne County, or Rhode Island’s Kent County—the prospect of further upheaval is anything but appealing. As Jeff Bust, a resident of Frankfort, Illinois, wrote in an op-ed for the Chicago Tribune, “I voted for Trump because he was the alternative to letting a collection of free spenders, organizers, race-baiters, intellectuals, tree huggers and professional value arbitrators continue to spend our grandchildren’s money.”55xJeff Bust, “I’m a Deplorable, and I’m Happy I Voted for Trump,” Chicago Tribune, February 3, 2017, http://www.chicagotribune.com/news/opinion/commentary/ct-trump-voter-happy-deplorable-perspec-0206-md-20170203-story.html.
Debate persists about which demographic mix best drives a city’s success. Urban theorist Richard Florida has become a powerful champion of what he calls the “creative class”: the young professionals drawn to hubs of innovation, often near institutions of higher learning—places such as Austin and North Carolina’s Research Triangle. By contrast, fellow theorist Joel Kotkin points to cities such as Houston and Salt Lake City, where the cost of living is low and regulations are comparatively lenient, making cities like these beacons for entrepreneurial immigrants. And while Kotkin frequently points out that many Americans continue to prefer suburban lifestyles, the headline remains the same: Urban America, once left for dead, is back.
But while this fifth Mumfordian migration seems to suggest a return to the past—we’re re-populating communities that prospered way back when Americans were moving from farm to factory—one crucial question persists: Will the basic building block of American community remain the same?
Similarly Situated Strangers
Today, without thinking much about it, champions of urbanism presume that the reinvigorated downtown will bring back the vitality that was lost when Americans abandoned the metropolitan core. It’s certainly true that the physical space that separates residents of suburbia collapses when they move closer to downtown. But what about the human connections that emerged in the colonial villages, frontier towns, and urban tenements of past eras? Will tomorrow’s urban landscape, laid out in what will likely be a form similar to that of the bustling cityscapes of previous decades, foster and harness the same sorts of social interactions? Or will this current migration mark a much more significant break with the past, one in which ordinary Americans embrace an entirely new and distinct portfolio of personal relationships?
Several decades ago, the Canadian scholar Marshall McLuhan coined a phrase that has since been so widely overused that it now sounds like the hollowest of clichés. Modern technology, McLuhan predicted, would eventually turn the world into a “global village.” By most conventional measures, his prediction has been borne out. As Tom Friedman and Michael Mandelbaum argued in their 2011 book That Used to Be Us, “In the span of a decade, people in Boston, Bangkok, and Bangalore, Mumbai, Manhattan and Moscow, all became virtual next-door neighbors.”66xThomas L. Friedman and Michael Mandelbaum, That Used to Be Us: How America Fell Behind in the World It Invented and How We Can Come Back (New York, NY: Picador, 2011), 63. Globalization has, without question, refashioned modern life.
But pithy as the phrase may be, “global village” is really a contradiction in terms. You can no more be a neighbor to someone who lives halfway around the world than you can be a spouse to a stranger. Someone could inscribe your name on a marriage certificate conferring the rights and obligations of matrimony to you and a random non-acquaintance. But a marriage, in any conventional sense, embodies a certain intimacy. And the same applies to a neighbor: Two people who live three or four doors away from each other share a certain body of knowledge that would be entirely unknown, and maybe unknowable, to someone who lived even a few dozen miles away.
The British anthropologist Robin Dunbar spent years researching isolated societies, both past and present. He discovered a remarkable similarity across geography and context. Human societies, he found, naturally sort themselves across three distinct levels of intimacy. The first, and most intimate, Dunbar labeled bands. These are the people who sleep together in overnight camps and know one another intimately. They rarely number more than a few dozen together. At the other end of the intimacy spectrum are tribes, groupings that live under the broadest and thinnest common banner. Fellow tribe members may share in certain rituals and traditions, but they rarely know one another personally.
Situated squarely between bands and tribes are what Dunbar termed villages. A village, generally speaking, marks a collection of bands, and groups of villages constitute a tribe. Correspondingly, fellow villagers are rarely as intimate with one another as they are with fellow members of their band, but they are more intimate than they would be with outside members of their tribe. Villagers do not necessarily know one another personally—but they are often able to converse about something specific. They’d know if someone’s mother were ill, or if their child had achieved an outstanding feat. Upon seeing one another, their conversation would flow from a common frame of reference.77xRobin Dunbar, “Coevolution of the Neocortical Size Group Size, and Language in Humans,” Behavioural and Brain Sciences 16, 1993, 681–735.
What held the American community together through its first four migrations was a very specific and shared sociological architecture. Colonial villages, frontier towns, urban tenements, and even some first-ring suburbs were classic examples of Dunbarian villages in that they were suffused by familiar, but non-intimate, relationships. The vicissitudes of ordinary life made it almost inevitable that people who lived near one another would be socially connected. It wasn’t just, as Alexis de Tocqueville wrote in the 1830s, that Americans were unusually likely to join voluntary associations. The demands of democratic government—the fact that power flowed up from the grassroots—prompted similarly situated strangers to get to know one another in pursuit of the common good.
Today’s reinvigorated cities boast much of what made urban America so vibrant during its heyday. The cultural amenities, the coffeehouse culture, the vast diversity, and even the convenience of public transit have emerged in places for which, in the mid-1970s, conventional wisdom predicted continued decline. But one feature distinguishes today’s urban meccas from those of eras past. The core sociological building block that Jane Jacobs celebrated in The Death and Life of Great American Cities—the Dunbarian village instantiated in an urban neighborhood—has all but collapsed.
A Different Social Architecture
That’s not to say that the institutions of urban neighborhoods have disappeared. Cities are still replete with neighborhood councils and community boards. Realtors and community associations demarcate the urban landscape with equal diligence (even if with different motives). Many schools, particularly private ones, still draw students from families that live in certain parts of town. But each of those attributes can be distinguished by its distance from what is the most vital characteristic of any neighborhood: mutual familiarity.
Do residents know one another well enough to care for one another in moments of need? Do they know enough to ask about a sick family member or a troubled young student? If the people who live in apartments on the same hallway bumped into one another in the grocery store, would they be able to ask a question about something more personal than the weather? In too many instances today—and almost certainly in a greater percentage of cases than in previous eras—the answer is no. With much greater frequency, neighbors have become, for want of a better phrase, similarly situated strangers.
That’s not to suggest that city dwellers today are entirely cut off from the rest of the world. They haven’t become automatons, despite the fears that coalesced in response to the finding reported by Robert Putnam in his 2000 work of social analysis, Bowling Alone: The Collapse and Revival of American Community. A more accurate characterization would be that today’s metropolitans are as cosmopolitan as ever: They’re deeply connected to the people they love. Many are helicopter parents, constantly engaged in supervising their children’s progress from moment to moment. And they are simultaneously members of vast networks, keeping track of hundreds of old acquaintances on social media in a way their grandparents would never have thought possible.
But in the competition for time between band, village, and tribe, the former and latter have claimed much more of each individual’s time and attention. Lost at the expense of those relationships in the middle are the friendly but non-intimate ties that once connected people who saw each other at PTA meetings, on bridge night, at the Elks Club, or when the folks across the street came over for a Sunday afternoon cookout. Much as Americans today shudder at the prospect of being “judged” by the people who live nearby, we shouldn’t entirely dismiss the benefits of knowing the people who make up the surrounding community.
For six years, from 2007 to 2013, my wife and I lived in one of several apartments carved out of an old brownstone near Dupont Circle in Washington, DC. By most measures, the neighborhood was (and is) an archetypal urban success story: recently gentrified, pedestrian friendly, transit accessible, and thick with bars, coffee shops, and brunch-oriented restaurants. If a New Urbanist were looking for a model community to copy in other cities, he or she would do well to draw from this slice of Washington.
It’s not that I want to suggest that there were no neighborly relationships in our old neighborhood. We had a handful of friends. We connected with a couple that lived a floor below and one that lived a floor above. But the pervasive feeling when I walked our dog around the same four blocks every morning wasn’t one of neighborly familiarity. Rarely did I nod at a familiar face or bump into a friendly acquaintance. More often, men and women on the street avoided eye contact, lost in their earbuds as they scurried quickly by. My sense then was that, much as we all enjoyed the same neighborly amenities, we were doing so less as a connected community and more as proximate strangers. We shared all the geographic attributes of neighborliness. But we rarely, if ever, interacted.
Certainly, there were others who would have reported having much deeper connections to the neighborhood. And those proximate strangers were hardly isolated: Many, like my wife and me, were thoroughly connected to family members, friends, and peers in communities near and far. Indeed, they were likely more connected to those more and less intimate acquaintances than their grandparents had been to corresponding ties. But most had let neighborly relationships wither.
The data indicates a powerful trend. As Harvard sociologist Peter Marsden explained to me, the General Social Survey, the ongoing project of a research organization based at the University of Chicago, is an excellent tool for understanding how individuals invest their time and attention. Asked with whom they’ve spent a “social evening” during the previous months, Americans provide evidence that they have largely kept up with family and friends who live elsewhere. But the percentage of Americans reporting a social evening with a neighbor has plummeted. In other words, cities may be coming back to life—but they’re being rebuilt with a very different social architecture.
To be sure, this shift is not universal. The experience differs from community to community and person to person. And those caveats often point to important distinctions. As Putnam’s more recent work has demonstrated, the level of social capital has a broadly inverse relationship with the degree of diversity. In other words, Americans who live in proximity to people whose ethnic or racial background is different from their own are less likely to be engaged with their neighbors. Conversely, the people living in more homogenous neighborhoods—perhaps, in some cases, communities put most at risk by gentrification—are more engaged with the people who live nearby. As Putnam explains “People living in ethnically diverse settings appear to ‘hunker down’—that is, to pull in like a turtle.”88xQuoted in Michael Jonas, “The Downside of Diversity,” Boston Globe, August 5, 2007, http://archive.boston.com/news/globe/ideas/articles/2007/08/05/the_downside_of_diversity/.
That finding raises a particularly vexing question: As cities grow and, in many cases, become more diverse—as the children and grandchildren of people who fled to the suburbs settle closer to downtown—will urban communities retain all the magic of close-knit diversity absent the benefit of neighborly familiarity? We can certainly hope they will. But we should consider the possibility that some of what we would want from a new age of cities won’t materialize. The contingent aspects of urban life celebrated by Jane Jacobs in The Death and Life of Great American Cities were born not just of urban design but of a certain sociological reality. And in the event that Americans live in proximity to strangers (rather than neighbors), the great promise of the urban age may prove elusive.
A Missing Ingredient
Consider the nation’s current frustration with domestic politics. Analysts across the political spectrum tend to embrace a familiar litany of complaints. Talk about the poor quality of today’s national leaders often glosses over the failings of yesterday’s politicians—and gives too little credit to the men and women who now aspire to public service. Beyond that, pundits tend to blame institutional factors that existed even before government seemed to become so hopelessly gridlocked: money in politics, special interests, gerrymandering, the filibuster, balkanized media. A quick trip through history makes clear that none of those elements are new to American democracy, even if they may be contributing to today’s dysfunction.
What is new? The absence of neighborly relationships. Tocqueville noted in the 1830s that Americans could be distinguished from Europeans in large part because they displayed a preference for local, bottom-up solutions; that was among the reasons the inhabitants of the “new” world were unusually apt to join voluntary associations. That mutual familiarity bred an unusual openness to collaborative solutions. You might not like or agree with your neighbor, but you could understand why someone might hold an opposing viewpoint. You might want to raise taxes to pay for a new amenity, or to reduce environmental regulation to attract new business—but neighborly relationships would help you appreciate any argument’s flip side. Often, such familiarity leads to compromise.
Absent such familiarity, an ordinary person is more likely to see a political adversary as an apostate. And if the other point of view is heretical, any ally looking to compromise becomes a heretic. In his work on deliberative polling, Stanford political scientist James Fishkin has demonstrated how powerful personal interactions are in any democratic setting: Roughly three-quarters of the time, in polls taken before and after members of a divided community speak in some depth with people who hold the opposing view, the results change substantially.99xJames S. Fishkin, When People Speak: Deliberative Democracy and Public Consultation (New York, NY: Oxford University Press, 2009), 96–97.
Neighborliness may not be an avenue to universal comity, but friendly face-to-face interactions can ease a gridlocked political dynamic. So we have to wonder whether an urban landscape devoid of those most American of relationships will produce the kind of forbearance and mutual understanding that once fostered compromise and cooperation amid diversity.
Second, and maybe a source of just as much concern, is the question of American entrepreneurship. Without a great deal of notice, tallies of business startups, particularly among millennials, suggest that everyday commercial risk-taking is on the wane. Some of that may be attributable to factors variously cited on the left and right: regulatory burdens, insufficient access to capital, failing educational institutions, regional imbalances in the distribution of venture capital funding. But there’s another possibility: Even though they live in proximity to a wide range of people with different perspectives and experiences, Americans are seldom exposed to ideas outside the silos of their own experience. Neighborly conversations might puncture the bubbles that otherwise develop when you talk almost exclusively either to your closest acquaintances or your similarly oriented peers.
As Arthur Koestler wrote a half-century ago, “The creative act is not an act of creation in the sense of the Old Testament. It does not create something out of nothing; it uncovers, selects, re-shuffles, combines, synthesizes already existing facts, ideas, faculties, skills.”1010xArthur Koestler, The Act of Creation (London, England: Hutchinson, 1976), 120. First published 1964. Gutenberg combined the existing technologies of ink, movable type, and paper to create the printing press. Steve Jobs spliced together mobile telephony, graphical interfaces, and satellite connectivity to produce the iPhone. Neighborly connections were frequently the mundane avenues through which an expert in one field randomly encountered a new concept. Today, in the absence of that exposure, the likelihood of combining various new ideas in novel ways has dwindled.
None of this is to say that the next generation of vibrant cities won’t find alternative means to similar ends. By definition, the urban landscape puts individuals with potentially divergent political positions and disparate fields of expertise in propinquity. And if new technologies emerge to drive interaction at a neighborhood level—Nextdoor, for example, is creating a social network that connects would-be strangers who live near one another—the magic sown within the individual building blocks of American community may well survive.
But we should also be aware of another possibility. Within the context of the various Mumfordian migrations—from east to west and from farm to factory—the most disruptive may prove to be this most recent revolution. When President Jimmy Carter walked through the ruins of the South Bronx in the late 1970s, anyone predicting today’s urban renaissance might have been viewed as a false prophet. But accolades for the “triumph of the city” proclaimed by Edward Glaeser need to be tempered by acknowledgment of an unexpected challenge: In cities where neighbors remain strangers, the crucial ingredient of a thriving American community will be missing.