Christine Emba edits The Post’s In Theory blog.

“No one saw the Great Flood coming,” the first chapter ominously begins.

In “The Benedict Option,” a much-discussed new book describing itself as “a strategy for Christians in a post-Christian nation,” author Rod Dreher explores the implications of the cascade of Americans leaving organized religion — the number of religiously non-affiliated climbed to 23 percent in 2014 from 16 percent in 2007 — and the squeezing out of traditionally minded Christians from public life.

The book’s verdict on today’s culture is grim. Drawing from the work of philosopher Alasdair MacIntyre, Dreher describes modern society as “governed not by faith, or by reason, or by any combination of the two.” The picture is of an America deep in the grip of an unstable late modernity, a society that has become chaotic, fragmented, dissolute and increasingly hostile to traditionally minded Christians.

True, some of the book’s descriptions of imminent persecution and a fast-approaching End of the West are overwrought, and it’s written to appeal first and foremost to a conservative, religious audience. But the observations and advice offered in “The Benedict Option” shouldn’t be shrugged off by everyone else. In fact, they ought to be thoughtfully considered by anyone worried about creating and preserving a healthy U.S. society, whether they spend Sundays at brunch or in the pews.

Many of the contentedly progressive would like to think that backing away from the strictures of religion has done our country a world of good. In fact, the opposite may be true. For one thing, there’s the matter of simple social cohesion: Increasing secularization can often lead to less tolerance, not more. As Americans on the right and left untether themselves from the standards of organized religion, they often redraw their allegiances more broadly, rallying around identities of race or nationalism while setting aside tempering ideals such as charity and forgiveness. Think of the alt-right, the small, far-right movement that seeks a whites-only state, suspicious of Christianity because of its acceptance of many groups, or violent protesters on the left, more interested in tearing down their opponents than seeking opportunities for reconciliation. Such attitudes lead to a more partisan politics and more vicious public life.

On an individual level, becoming increasingly unmoored from traditions and norms leads more frequently to negative outcomes than positive ones. Witness the sharply growing numbers of middle-age, working-class Americans — those most likely to have lost their connections to the habits and support systems religious engagement tends to build — dying from what researchers are calling “deaths of despair”: enough of them to lower U.S. life expectancy for the first time in decades.

It’s not necessarily true that Christian communities are flourishing in contrast to the rest of society; in fact, it’s a major conceit of the book that most are not. But in the face of the great unmooring, Dreher advocates that those who are serious about their faith act to embrace a sort of “exile in place” and commit to strengthening their families, churches and schools, forming a vibrant counterculture that will preserve Christianity despite a rising tide of secularism. His strategies for doing so would also benefit society at large.

The title of “The Benedict Option” is inspired by St. Benedict of Nursia, who founded the Western tradition of monasticism after leaving a fallen Rome in the 6th century. Benedict’s Rule — originally for monks, but suggested in the book for the everyday Christian — involves an embrace of community, stability and hospitality alongside a thoughtful ordering of one’s days. Meet the neighbors; create anchors of place; foster structures of personal discipline. Any of these would benefit believers and nonbelievers alike as anomie and loneliness become both more common and more deadly.

Other strategies for ostensibly Christian survival are similarly relevant to a broader audience. Addressing our attitudes toward work, Dreher proposes deprioritizing headlong professional advancement in favor of a more balanced, integrated life in which faith and community take precedence. This is worth considering even if faith isn’t a factor: Shifting work from the center of our existence would allow more space for family, community and our own mental health, and would leave us less susceptible to the ravages of an unfeeling market.

The book also makes a fascinating case for rethinking our political life. Dreher urges Christians to recognize that conventional politics won’t save them and that the current system is fundamentally inadequate to the challenge of fixing the bigger problems of society and culture. His alternative is one we could all embrace: Do what can prudently be done within the existing order, but direct more attention to creating parallel structures that will better serve society. Turn off the TV and log off Twitter, and instead join the volunteer fire department. Rather than depending on major parties to defend your values, consider the power of ordinary change.

To some, the premise of “The Benedict Option” — that Christianity in the United States is in danger of disappearing — may elicit a shrug. But in the face of a rising tide of isolating modernity, Dreher’s survival strategies are relevant to us all.