Evaluating the evidence on micro-aggressions and trigger warnings

MORE than 150 years ago, John Stuart Mill put forward a sensible proposition. “The only purpose for which power can be rightfully exercised over any member of a civilised community, against his will, is to prevent harm to others,” he wrote in On Liberty. First Amendment law has hewed closely to Mill’s harm principle, permitting all sorts of disreptuable speech and behaviour that do not pose an imminent physical threat. Campus protesters, by contrast, argue that some speech causes psychological harm, and is therefore covered by Mill’s dictum. Do those claims withstand academic scrutiny?