In May, Jack Peterson went on a Tinder date. With a woman. They ate at an Italian restaurant in downtown Chicago, and made casual chitchat about themselves. It was an ordinary date in every way. But for 19-year-old Peterson, it was an achievement of epic proportions. Until recently, Peterson identified as an “incel,” or involuntarily celibate. Incels believe that, due to reasons entirely beyond their control ― too short, too bald, too weak a jawline ― they cannot attract a female partner. They believe they’re doomed to remain alone, forever. For many incels, this fatalistic worldview is paired with a...