We live in a logic-obsessed world, from computer modelling of the economy to businesses run by spreadsheets. But we also know, from decades of behavioural economics and evolutionary psychology research, humans are not robots. The social world is not a machine but a complex system. In Alchemy: The Surprising Power of Ideas that Don’t Make Sense, Rory Sutherland, vice chairman of Ogilvy and columnist for The Spectator, explains how to crack the magic underlying our humanity.