When President de Gaulle was asked to authorise the criminal prosecution of Jean-Paul Sartre for civil disobedience during the Algerian war, he declined. ‘One does not lock up Voltaire,’ he added, unhistorically. In France, ‘public intellectuals’ have a quasi-constitutional status, so it’s not surprising that a furious bunfight has broken out over a handful of philosophers known as ‘les nouveaux réactionnaires’.