In the opening sentence of his novel Anna Karenina, Leo Tolstoy says that “all happy families are alike, but each unhappy family is unhappy in its own way.” In commenting on this passage, the historian Paul Johnson disagrees, retorting that the sources of unhappiness in families—alcoholism, infidelity, violence, poverty—are tiresome and common and lead to tiresome, common, and sad results.7 The commonality of problems is great news, though, because the commonality of the afflictions allows common approaches to alleviating them.