John Jabez Edwin Mayall · Public domain

A philosopher who turned economics into a theory of history: that societies are shaped by who controls production and who does the producing, and that capitalism would generate the very class conflict that destroys it. Co-wrote The Communist Manifesto with Friedrich Engels in 1848 and spent much of his London exile writing Das Kapital, a systematic critique of capitalist economics unfinished at his death. Expelled from Prussia, Belgium and France for his politics before settling in England, he never held power himself, but the intellectual movement built on his ideas reshaped the twentieth century.