Popper, Karl Raimund

British philosopher of science, who was born in Austria and became a naturalized British subject in 1945. His theory of falsificationism states that although scientific generalizations cannot be conclusively verified, they can be conclusively falsified by a counterinstance; therefore, science is not certain knowledge but a series of ‘conjectures and refutations’, approaching, though never reaching, a definitive truth. For Popper, psychoanalysis and Marxism are unfalsifiable and therefore unscientific.

Popper is one of the most widely read philosophers of the 20th century. His book The Open Society and its Enemies (1945) became a modern classic. In it he investigated the long history of attempts to formulate a theory of the state. Animated by a dislike of the views of Freud and Marx, Popper believed he could show that their hypotheses about hidden social and psychological processes were falsifiable.

His major work on the philosophy of science is The Logic of Scientific Discovery (1935). Other works include The Poverty of Historicism (1957) (about the philosophy of social science), Conjectures and Refutations (1963), and Objective Knowledge (1972).

Popper was professor of logic and scientific method at the London School of Economics (LSE) 1949–69. He was knighted in 1965.