The murder last week of the Catholic priest Jacques Hamel as he celebrated morning Mass in a church in the suburb of the French city of Rouen showed that Islamic State is the most aggressively innovative of the serious challenges that democratic societies confront today.
The violent act broke two powerful taboos. The first was that a priest was killed while kneeling at the altar in a chapel. Church sanctuary, recognized as a refuge of safety from the Middle Ages through the 17th century, no longer has any legal force. Yet, its breach still shocks.
Catholic priests have been murdered in large numbers through the ages — at the hands of Protestants (it was mutual), Muslims, communists and Nazis. But the isolated fact of a savage murder on a suburban summer morning stuns by its immediacy, and by being bathed in artificial light by the news media.