Karl Popper

Karl Raimund Popper (1902-1994) made decisive contributions to twentieth-century philosophy of science and political philosophy. Born in Vienna to a middle-class Jewish family — his lawyer father kept a personal library of over 12,000 volumes — Popper described his upbringing as decidedly bookish.

A brief teenage flirtation with Marxism ended in 1919 when Vienna police shot demonstrators from his party. The episode left him permanently suspicious of historicism — the idea that history develops according to inevitable laws. He took a Vienna doctorate in 1928 and taught at a secondary school for six years.

Logik der Forschung (1934) introduced his criterion of falsifiability. Where the logical positivists demanded verifiability for meaning, Popper insisted any scientific statement must specify in advance what observation could refute it. He used this to disqualify Freudian psychoanalysis, Adlerian individual psychology, and Marxist historical theory as pseudoscience: each could explain any observation.

In 1937, with the Anschluss looming, Popper accepted a post in New Zealand at Canterbury. Exile produced his other masterpiece, The Open Society and Its Enemies (1945), a fierce attack on Plato, Hegel, and Marx as defenders of "closed" societies, and a defense of piecemeal social engineering. Seventeen of his Jewish relatives died in Nazi camps.

After the war, Popper joined the LSE and was knighted in 1965 on Bertrand Russell's recommendation. His student George Soros read The Open Society as an LSE student and later named his charitable network the Open Society Foundations after it. Nassim Taleb has likewise credited him as a major influence. The 1965 London symposium with Thomas Kuhn over Structure of Scientific Revolutions staged the most consequential debate in twentieth-century philosophy of science. Popper died in 1994, aged 92.