People who haven't experienced a friendship like this firsthand may not even realize they've seen one before, although they've likely known others who've had one and can recognize it when it's pointed out. It was common for friends and acquaintances I told about this book to recall, as if an aha thought bubble had bloomed above their heads, an aunt or a grandmother who shared a house with a friend until the end of life. Doctors who worked with older patients told me that frequently the person at a dying patient's bedside is not a spouse or relative but a longtime, dear friend.

I started working on this book with the simple desire to bring attention to these friendships. My friendship with M made the world pulse with more possibilities for intimacy and support than before, and I wanted others to feel those possibilities for themselves. As I talked to people who had devoted, life-defining friendships, I heard stories like Andrew and Toly's, about how their loved ones sometimes reacted with confusion or suspicion. I began to see how these unusual relationships can also be a provocation—unsettling the set of societal tenets that circumscribe our intimate lives: That the central and most important person in one's life should be a romantic partner, and friends are the supporting cast. That romantic love is the real thing, and if people claim they feel strong platonic love, it must not really be platonic. That adults who raise kids together should be having sex with each other, and marriage deserves special treatment by the state.

Challenging these social norms is not new, nor are platonic partners the only dissidents. People who are feminists, queer, trans, of color, non-monogamous, single, asexual, aromantic, celibate, or who live communally have been questioning these ideas for decades, if not centuries. All have offered counterpoints to what Eleanor Wilkinson, a professor at the University of Southampton, calls compulsory coupledom: the notion that a long-term monogamous romantic relationship is necessary for a normal, successful adulthood. This is a riff on the feminist writer Adrienne Rich's influential concept of "compulsory heterosexuality"—the idea, enforced through social pressure and practical incentives, that the only normal and acceptable romantic relationship is between a man and a woman. Some of the first stories we hear as children instill compulsory coupledom, equating characters finding their "one true love" with living "happily ever after." In a society governed by compulsory coupledom, those who aren't one half of a couple can feel excluded. Meg, an artist in her seventies who I got to know while working on this book, told me about the period when her friends married off and she was relegated to the "lunch slot." Dinner was reserved for their husbands. I've heard from single people a generation or more below Meg that they've felt others have demoted them, treated them like "an extra" or as immature—like a train that stalled before reaching the station of full adulthood. The privileging of romantic relationships, thoroughly documented by scholars, pervades not just our social norms but also the law; to give an example, Americans can extend health insurance and Social Security benefits to spouses but not to the closest of friends.

Just as compulsory heterosexuality disregards people's experiences of same-sex attraction, compulsory coupledom ignores the large number of people who aren't in a romantic unit. For the last few decades, the age of first marriage has steadily ticked upward, as young people look to financially establish themselves and feel certain about their compatibility with a partner before signing up for devotion until death. While some people are heading down the aisle later, others aren't getting married at all. Only about half of adults in the US ages twenty-five to fifty-four are currently married, down from 67 percent a few decades ago. At the same time, the share of adults in this age group who have never married has increased to nearly one-third. And marriage has practically become a status symbol, attainable primarily by those with more education and money: wealthier Americans are more likely to marry than those with lower incomes. Americans are forgoing more than marriage; many don't come home to a romantic partner at the end of the day. According to 2019 data from Pew, 38 percent of American adults are neither married nor cohabiting with a partner, up from 29 percent in 1990.

One response to these changes has been to lament them and attempt to turn back the clock. Some politicians and policymakers have made impassioned pleas to encourage marriage while the US government has spent hundreds of millions of dollars on marriage promotion with little to show for it. In general, we should be wary of paternalism, but in this case, we have grounds to be particularly skeptical: the idealized romantic relationship rests on shaky ground.

That instability comes, at least in part, from modern expectations of romantic partnerships. One man I interviewed observed that many people he knows have a "one-stop shopping" approach to romantic relationships: get your sexual partner, confidant, co-parent, housemate, and more, all in the same person. Prominent experts have recognized this pattern and are concerned about it. "When we channel all our intimate needs into one person," the psychotherapist Esther Perel writes, "we actually stand to make the relationship more vulnerable." Such totalizing expectations for romantic relationships can leave us with no shock absorber if a partner falls short in even one area. While we weaken friendships by expecting too little of them, we undermine romantic relationships by expecting too much of them.

People who haven't experienced a friendship like this firsthand may not even realize they've seen one before, although they've likely known others who've had one and can recognize it when it's pointed out. It was common for friends and acquaintances I told about this book to recall, as if an aha thought bubble had bloomed above their heads, an aunt or a grandmother who shared a house with a friend until the end of life. Doctors who worked with older patients told me that frequently the person at a dying patient's bedside is not a spouse or relative but a longtime, dear friend.

I started working on this book with the simple desire to bring attention to these friendships. My friendship with M made the world pulse with more possibilities for intimacy and support than before, and I wanted others to feel those possibilities for themselves. As I talked to people who had devoted, life-defining friendships, I heard stories like Andrew and Toly's, about how their loved ones sometimes reacted with confusion or suspicion. I began to see how these unusual relationships can also be a provocation—unsettling the set of societal tenets that circumscribe our intimate lives: That the central and most important person in one's life should be a romantic partner, and friends are the supporting cast. That romantic love is the real thing, and if people claim they feel strong platonic love, it must not really be platonic. That adults who raise kids together should be having sex with each other, and marriage deserves special treatment by the state.

Challenging these social norms is not new, nor are platonic partners the only dissidents. People who are feminists, queer, trans, of color, non-monogamous, single, asexual, aromantic, celibate, or who live communally have been questioning these ideas for decades, if not centuries. All have offered counterpoints to what Eleanor Wilkinson, a professor at the University of Southampton, calls compulsory coupledom: the notion that a long-term monogamous romantic relationship is necessary for a normal, successful adulthood. This is a riff on the feminist writer Adrienne Rich's influential concept of "compulsory heterosexuality"—the idea, enforced through social pressure and practical incentives, that the only normal and acceptable romantic relationship is between a man and a woman. Some of the first stories we hear as children instill compulsory coupledom, equating characters finding their "one true love" with living "happily ever after." In a society governed by compulsory coupledom, those who aren't one half of a couple can feel excluded. Meg, an artist in her seventies who I got to know while working on this book, told me about the period when her friends married off and she was relegated to the "lunch slot." Dinner was reserved for their husbands. I've heard from single people a generation or more below Meg that they've felt others have demoted them, treated them like "an extra" or as immature—like a train that stalled before reaching the station of full adulthood. The privileging of romantic relationships, thoroughly documented by scholars, pervades not just our social norms but also the law; to give an example, Americans can extend health insurance and Social Security benefits to spouses but not to the closest of friends.

Just as compulsory heterosexuality disregards people's experiences of same-sex attraction, compulsory coupledom ignores the large number of people who aren't in a romantic unit. For the last few decades, the age of first marriage has steadily ticked upward, as young people look to financially establish themselves and feel certain about their compatibility with a partner before signing up for devotion until death. While some people are heading down the aisle later, others aren't getting married at all. Only about half of adults in the US ages twenty-five to fifty-four are currently married, down from 67 percent a few decades ago. At the same time, the share of adults in this age group who have never married has increased to nearly one-third. And marriage has practically become a status symbol, attainable primarily by those with more education and money: wealthier Americans are more likely to marry than those with lower incomes. Americans are forgoing more than marriage; many don't come home to a romantic partner at the end of the day. According to 2019 data from Pew, 38 percent of American adults are neither married nor cohabiting with a partner, up from 29 percent in 1990.

One response to these changes has been to lament them and attempt to turn back the clock. Some politicians and policymakers have made impassioned pleas to encourage marriage while the US government has spent hundreds of millions of dollars on marriage promotion with little to show for it. In general, we should be wary of paternalism, but in this case, we have grounds to be particularly skeptical: the idealized romantic relationship rests on shaky ground.

That instability comes, at least in part, from modern expectations of romantic partnerships. One man I interviewed observed that many people he knows have a "one-stop shopping" approach to romantic relationships: get your sexual partner, confidant, co-parent, housemate, and more, all in the same person. Prominent experts have recognized this pattern and are concerned about it. "When we channel all our intimate needs into one person," the psychotherapist Esther Perel writes, "we actually stand to make the relationship more vulnerable." Such totalizing expectations for romantic relationships can leave us with no shock absorber if a partner falls short in even one area. While we weaken friendships by expecting too little of them, we undermine romantic relationships by expecting too much of them.