Studio Harcourt. · Public domain

Raymond Aron spent decades as one of the sharpest critics of Marxism among France's intellectual class, arguing in his 1955 book The Opium of the Intellectuals that many French thinkers who prided themselves on criticizing capitalism were simultaneously excusing the crimes of Communist governments in the East. The stance made him an outlier among his peers and fueled his long, often prickly friendship with Jean-Paul Sartre — "better be wrong with Sartre than right with Aron" became a common jab at his expense. Aron wrote widely across sociology, political science and history over a career spent mostly resisting the intellectual fashions of his time.