Then Walford read an article about Sunday Assembly, a community started in Great Britain in 2013 that had spread quickly across the Atlantic to her doorstep. Members gather on Sundays, sing together, listen to speakers, and converse over coffee and donuts. Meetings are meant to be just like Church services—but without God. “That’s it,” she thought. “That’s what I want.”

When Walford shed her faith, she joined a large and fast-growing group—the “nones,” or the religiously unaffiliated. According to data from the latest version of the Public Religion Research Institute’s annual “American Values Atlas,” 25 percent of Americans today are religiously unaffiliated, up from single digits in the 1990s. Among young people, that number is 39 percent. Those numbers describe not just a retreat from organized religion, but also an erosion of community. Many faith congregations have acted as social anchors in their areas, providing a place to see and be seen by the same friendly faces each week. As these and other traditional social supports hollow out, Americans are left “bowling alone,” as the political scientist Robert Putnam famously put it.

Secular congregations such as Sunday Assembly and Oasis—a similar group started in 2012—seek to offer a solution. Both were founded by faithless seekers hoping to carry on certain aspects of religious life: the community, the moral deliberation, and the rich sense of wonder. When they were growing so rapidly in their early years, these congregations were heavily covered by media outlets. “The Hot New Atheist Church,” gushed a 2013 Daily Beast headline about Sunday Assembly. HuffPost noted that the number of assemblies had doubled in a single weekend in 2014. The media coverage emphasized the new community’s high-energy services, its celebratory message, and the top-of-your-lungs group renditions of pop anthems such as “Livin’ on a Prayer.” For those uncomfortable with the level of overt spirituality even within relatively liberal denominations, such as Unitarian Universalism, secular communities offered a different option.

But even as the growth of “nones” has revved up in the intervening years, the growth of secular congregations hasn’t kept pace. After a promising start, attendance declined, and nearly half the chapters have fizzled out—including the New York one that Walford joined. Building a durable community of nonbelievers, it turns out, is more complicated than just excising God.

If the sudden emergence of secular communities speaks to a desire for human connection and a deeper sense of meaning, their subsequent decline shows the difficulty of making people feel part of something bigger than themselves. One thing has become clear: The yearning for belonging is not enough, in itself, to create a sense of home.

The New York Sunday Assembly was everything that Justina Walford had been hungering for since leaving her faith. Meetings involved “sermons” from scientists, artists, and academics; members sang pop songs together and snapped their fingers to poetry readings. Old-timers chatted by the snack table and invited newbies to meals outside the group. “I just fell in love with it,” Walford said. “I loved the singing … I loved the interaction. I loved once a month seeing the same people.” She became an organizer, one of the leaders of the chapter working long volunteer hours to put each service together. That lasted for a couple of years—and then things began to fall apart.