One afternoon, at the church library, a friend and I got into a conversation about what makes a man. Not so much the biology—what makes male different from female—as about what makes man different from boy.

Was it as simple as age? Or as superficial as appearance? Or did it come down to how many attributes he fulfilled as defined by Art of Manliness? Who's to say what the standard is, anyway—are you looking to judge this according to the holy book, or by the stick of our society and culture? (And God knows the latter has given us everything—from toxic hyper-masculinity to passive emasculation—but the answer.)

At one point we rattled off a bunch of people we knew. Look at this guy, he said. He has a steady job, a wife and two kids. He takes good care of his body and fixes things around the house. Agreed—he's a man. This other guy...he's living at home with his parents, struggling to make ends meet. He hasn't figured out a direction for his life. He calls him a boy.