Immanuel Kant summed up The Enlightenment as ‘man’s emergence from his self-imposed immaturity.’ Apart from the gendered language, what else is there not to like? Quite a lot, it seems. The Enlightenment has been copping a bad rap for some time, with critics from feminists to social conservatives. How could such a formative epoch in human civilisation fall so low in intellectual standing? And how might rediscovering the French fab four—Diderot, Rousseau, Montesquieu, and Voltaire— help repair the damage?