Karl Popper
Philosopher of science who championed falsification and open society.
Karl Popper was an Austrian-British philosopher and social commentator, born in Vienna in 1902 to a well-off, bookish family of Lutheran converts. He is best known for turning the scientific method on its head: instead of trying to prove theories true, he argued that science advances by trying to prove them false. This idea, called falsification, became his core criterion for distinguishing genuine science from pseudoscience. Popper insisted that no empirical theory can ever be definitively proven, but it can—and should—be tested by experiments that might show it wrong. He founded the philosophy department at the London School of Economics and is considered one of the most influential philosophers of science of the 20th century.
Politically, Popper was a fierce defender of liberal democracy and open societies. He opposed totalitarianism, communism, nationalism, fascism, and historicism, seeing them as irrational and reactionary. He believed that the best political systems are those that allow for open criticism and gradual reform. His own philosophy, which he called critical rationalism, rejected the idea that knowledge needs a secure foundation; instead, it embraced constant questioning and critique.
Popper’s early life was shaped by his family’s intellectual atmosphere and his own political awakening. He briefly embraced Marxism as a teenager, but after witnessing police kill unarmed socialist protesters in 1919, he abandoned the ideology and became a lifelong social liberal. He worked various jobs—street construction, cabinetmaking, and even in a children’s clinic run by Alfred Adler—before earning a doctorate in psychology in 1928. He then taught mathematics and physics in secondary school.
Fearing the rise of Nazism, Popper wrote his first major book, *The Logic of Scientific Discovery*, published in 1934. In it, he attacked inductivism, psychologism, and logical positivism, laying out his theory of falsifiability. In 1937, he escaped Europe for New Zealand, where he taught at Canterbury University College. There he wrote *The Open Society and Its Enemies*, a powerful critique of totalitarian thought and a defence of liberal democracy. He later moved to the United Kingdom, where he spent the rest of his career. Popper died in 1994.
- born
- 28 July 1902, Vienna, Austria-Hungary
- died
- 17 September 1994, Kenley, Surrey, England
- field
- Philosophy of science, political philosophy
- nationality
- Austrian–British
- known_for
- Falsifiability criterion, critical rationalism, defense of open society
Verified Timeline
Lore & Background
Popper was born in Vienna in 1902 to upper-middle-class parents. All of his grandparents were assimilated Jews; the Popper family converted to Lutheranism before he was born and so he received a Lutheran baptism. His father, Simon Siegmund Carl Popper, was a lawyer from Bohemia and a doctor of law at the Vienna University, and a bibliophile who had 12,000–14,000 volumes in his personal library. Popper left the Realgymnasium at 16 and began attending lectures in mathematics, physics, philosophy, psychology and the history of music as a guest student at the University of Vienna. In 1919, he became attracted by Marxism and joined the Association of Socialist School Students, but after the street battle in the Hörlgasse on 15 June 1919, when police shot eight of his unarmed party comrades, he turned away from historical materialism and abandoned the ideology. He worked as a cabinetmaker, completing an apprenticeship as a journeyman, and did voluntary service in one of psychoanalyst Alfred Adler's clinics for children. In 1928, Popper earned a doctorate in psychology under Karl Bühler, with Moritz Schlick as the second chair. Fearing the rise of Nazism and the threat of the Anschluss, he wrote his first book, Logik der Forschung (The Logic of Scientific Discovery), published in 1934, which criticised psychologism, naturalism, inductivism, and logical positivism, and put forth his theory of potential falsifiability as the criterion demarcating science from non-science. In 1937, he emigrated to New Zealand, becoming lecturer in philosophy at Canterbury University College, where he wrote The Open Society and Its Enemies. In 1946, after the Second World War, he moved to the United Kingdom to become a reader in logic and scientific method at the London School of Economics, and in 1949 was appointed professor of logic and scientific method. He retired from academic life in 1969, though he remained intellectually active for the rest of his life. Popper died of complications of cancer, pneumonia and kidney failure in Kenley at the age of 92 on 17 September 1994.
Reader's Guide
Popper's significance lies in his transformation of the philosophy of science through the principle of falsifiability: a theory in the empirical sciences can never be proven, but it can be falsified, meaning it can and should be scrutinised with decisive experiments. He replaced the classical justificationist account of knowledge with what he called 'the first non-justificational philosophy of criticism in the history of philosophy', namely critical rationalism. In political discourse, he is known for his vigorous defence of liberal democracy and the principles of social criticism that he believed made a flourishing open society possible. His political thought resides within the camp of Enlightenment rationalism and humanism. He was a dogged opponent of totalitarianism, communism, nationalism, fascism, historicism, and other reactionary and irrational ideas, and identified modern liberal democracies as the best-to-date embodiment of an open society. Popper founded the Department of Philosophy at the London School of Economics and Political Science. He was knighted by Queen Elizabeth II in 1965, elected a Fellow of the Royal Society in 1976, and invested with the insignia of a Member of the Order of the Companions of Honour in 1982.
Did You Know?
- Popper's father had a personal library of 12,000–14,000 volumes, which Popper inherited.
- After a street battle on 15 June 1919 where police shot eight unarmed comrades, Popper abandoned Marxism.
- Popper completed an apprenticeship as a cabinetmaker and worked as a journeyman.
- He earned his doctorate in psychology in 1928 under Karl Bühler, with Moritz Schlick as second chair.
- Popper was knighted by Queen Elizabeth II in 1965 and invested as a Member of the Order of the Companions of Honour in 1982.
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