When my two sons, now young adults, were in elementary school, on some days my wife and I were sure they were lying with completely straight faces when we interrogated them about the status of homework or chores or the shattered heirloom they were told never to touch. Then, before we could regroup, they were telling us about a new kid they befriended in school or any of a dozen other unexpected angelic deeds we assumed they would always be too self-centered to do. Yes, I’m exaggerating. Our...