A new book argues that if the institution of marriage is to endure, it must evolve with the times.

With infidelity now seeming less like a deadly plague and more like a relatively mild form of cancer—we all know someone who has suffered from it, even if we haven’t experienced it ourselves—does it still make sense for monogamy to constitute the basis for marriage? Or should couples figure out creative ways to expand the boundaries of their relationships, acknowledging that they might want to continue to be life partners even if one or both needs the occasional night off? This is the argument of Pamela Haag’s new book, Marriage Confidential: The Post-Romantic Age of Workhorse Wives, Royal Children, Undersexed Spouses, and Rebel Couples Who Are Rewriting the Rules, in which “affair-tolerant” couples aren’t a regressive throwback—they’re the benchmark of a new kind of modernity. Its abundance of gimmicky catchphrases aside, this book asks serious questions about whether we have come to expect too much from contemporary marriage: a partner who is simultaneously an emotional and intellectual “soul mate,” a monogamous provider of sexual thrills, and a best friend to see us through our creaky final decades. If marriage has a hard time living up to these burdens—and a divorce rate holding steady at 50 percent suggests just how hard it is—maybe we ought to be thinking about ways to transform it.

Haag notes that marriage has undergone a dramatic transformation from the “traditional” partnerships of the nineteenth century, when marriage was “a social institution and an obligation,” to the “romantic” marriages of the twentieth century, when the practice of choosing a partner for reasons of love rather than practicality first became widespread. Now, she argues, we are moving into a “post-romantic age.”

In a series of chapters examining monogamy alternatives that range from asexuality to open marriage, the only real target of her scorn is the serial monogamist, who’s “always convinced that he’s in love with the next girlfriend … and that it will be different for them, in this marriage, this time around.” If he’d stop chasing this fantasy of romantic love, she reasons, he could maintain an intimate partnership with his wife—even if only for the sake of their kids—while enjoying a discreet dalliance now and then. In this vision of marriage, the happiest couples might well be the “infidelity tolerators”: those who can accept a one-night stand or three as long as the marital bond is the primary relationship.

The problem isn’t only that “infidelity tolerance” is a slippery slope: One day, you’re quietly overlooking a suspicious text on your husband’s phone, the next you’re fielding questions from the news media about his love child. It’s also that this “post-romantic” view of marriage isn’t entirely convincing. Granted, it’s impossible to know what goes on within the privacy of other people’s marriages. But, while they may be getting rarer and rarer, we all know couples who seem to be happily, enduringly married: the elderly couple who hold hands in the street, or the assisted-living resident whom I once heard proudly brag that she and her husband had had sex every day of their marriage. “What is a mystery to me,” Haag confesses, “and a thing of beguiling beauty, is the genuinely sexually contented long-term marriage—a monogamous dam lovingly constructed to manage the wayward lusts of nature.” Unfortunately, it’s the one phenomenon of contemporary married life that she chose not to investigate. But the fact that it still exists suggests that the old rules might have some value yet.

Excerpted from Ruth Franklin’s (at The New Republic) article “Can (This) Marriage Be Saved?