On either side of the Atlantic, groups of public intellectuals have issued a call to arms. The besieged citadel in need of defending, they say, is the one that safeguards science, facts and evidence-based policy. These white knights of progress – such as the psychologist Steven Pinker and the neuroscientist Sam Harris – condemn the apparent resurgence of passion, emotion and superstition in politics. The bedrock of modernity, they tell us, is the human capacity to curb disruptive forces with cool-headed reason. What we need is a reboot of the Enlightenment, now.