The human brain is a remarkable organ. Honed by millions of years of evolution as we foraged in forests and savannahs, it is the ultimate survival computer. A finely tuned sympathetic nervous system allows us to respond quickly to danger; a natural instinct for grammar helps us communicate and collaborate.

But our foragers’ brains are not well suited to mathematics. They struggle with big numbers, they cannot easily grasp probabilities. So, for the most part, we base our instinctive judgments on heuristics — rules of thumb. In short, when it comes to economics, our intuition sucks.

The upshot is that all too often what feels instinctively right is straightforwardly wrong. A case in point is the conventional wisdom on inequality. Listen to any leading politician,