I didn’t even know he was married, let alone to her. By Kwame Anthony Appiah Kwame Anthony Appiah has been The New York Times Magazine’s Ethicist columnist since 2015 and teaches philosophy at N.Y.U.

You don’t have to know every detail of your friend’s relationship to sense that something’s…off. Maybe your bestie shrugs off her partner’s frequent texts like they’re no biggie (“He just worries when ...