In 1944, Theodor Adorno and Max Horkheimer published their famous claim that "Enlightenment reverts to mythology" - meaning that any rational order sooner or later collapses into irrationality. Seven decades later, with Brexit roiling the UK, a reality TV showman in the White House and batty conspiracy theories spreading like a plague, it seems that Adorno and Horkheimer were right on the money. How did we get here? Is human society fated to be irrational? And why is the alt-right having all the crazy fun these days?