The chattering class has a new fixation: polyamory. What began as a trickle of discourse a few years ago—as shows including Succession and Scenes From a Marriage streamed open relationships into our living rooms—has become a veritable flood. The past weeks and months have seen stories ranging from wide-eyed to prurient in The New Yorker, The New York Times, the Financial Times, NPR, The Wall Street Journal. At the center of the recent discussions is More: A Memoir of an Open Marriage, by Molly Roden Winter, an unsparing account of a polyamorous life—at least, a polyamorous life as lived by a white, wealthy, heterosexual Brooklynite. More—and the present interest in polyamory more broadly—is the result of a long-gestating obsession with authenticity and individual self-fulfillment. That obsession is evident today in Instagram affirmations, Goop, and the (often toxic) sex positivity of an app-dominated dating scene, but its roots go back decades. As the historian Christopher Lasch wrote in 1977, this worldview “assumes that psychic health and personal liberation are synonymous with an absence of inner restraints, …