Karl Popper

Today is the birthday of the philosopher of science Karl Popper, born in Vienna, Austria in 1902. Popper set out to explain what distinguishes scientific theories from nonscientific ones—essentially, science from pseudoscience. Yes there’s the scientific method, but that didn’t satisfy him; plenty of theories (Popper cited Marx’s theory of history and Freud’s psychoanalysis as examples) are supported by observation and empirical evidence but not necessarily scientific. Focusing on Einstein’s general theory of relativity, Popper proposed that scientific theories must be falsifiable—they must make “risky” predictions that, if they don’t show up in observations, refute the theory. “The scientific status of a theory is its falsifiability, or refutability, or testability,” he wrote. Popper is considered one of the greatest modern scientific philosophers.

Date in History: 28 July 1902