Bowling Alone, the title of Robert Putnam's 1995 article (later a bestselling book) perfectly captured a sense of national unease: Somewhere along the way, America had become a nation divided by apathy, and the bonds that held together civil society were disappearing. But while the phrase resonated with our growing sense of atomization, it didn't describe a new phenomenon. The fear that isolation has eroded our social bonds had simmered for at least two decades, when communitarianism first emerged as a cogent political philosophy. Communitarianism, as explained in the works...