Leo has sought to be a uniter calling for a more peaceful world. We need leaders who remind us of what is possible, who bring out the best in us while discouraging the worst.

To convey how all-encompassing the Roman Catholic Church was during the Middle Ages, the historian R.W. Southern once offered a striking analogy: The medieval church, he wrote in 1970, was “a compulsory society in precisely the same way as the modern state is a compulsory society.”