The surge in antisemitism caught a lot of commentators off guard. After the horrors of the 20th century, Western societies erected strong taboos against ethnic hatred, in particular against the oldest hatred. For a time, those taboos worked. By being sensitive to early-stage antisemitism (stereotyping, for example, or hinting at conspiracies), we made pogroms unthinkable.

Then, as if from nowhere, mobs were picketing and vandalizing Jewish shops, demanding that their Jewish neighbors condemn Israel and chanting, “Gas the Jews!” The Anti-Defamation League says antisemitic incidents are up by 30% and that the number of Americans with “highly antisemitic attitudes” has doubled. Human Rights Watch finds an equivalent rise in Europe, where synagogues and Jewish schools are routinely given armed guards.