Do you want free speech to thrive? Then it has to be regulated, now more than ever

Responses to the assault on Salman Rushdie have combined personal sympathy with a general defence of free speech. Sympathy should come first. The second remains controversial. Sticks and stones may break your bones, but what of “words can never hurt you”? Witness the Iranian government’s blaming of Rushdie himself and his supporters. It is he, not Iran, that lies hurt.

Freedom of speech is one of the most slippery concepts in political philosophy. John Stuart Mill pronounced it absolute but qualified it, as he did all liberties, where it causes “harm” to...