“To stay together and to know how to love each other for ever is the challenge Christian married couples face,” Pope Francis said during an unusual meeting on February 14—Valentine’s Day—with more than 10,000 engaged couples. The meeting, organized by the Pontifical Council for the Family, drew a far larger audience than Vatican officials had expected. Archbishop Vincenzo Paglia, whose office arranged the day’s events, conceded that “numbers are not everything,” but was clearly happy with the attendance of so many young couples, telling L’Osservatore Romano that “their enthusiasm says a lot.” The day’s events began with a series...