Karl Popper
Austrian-British philosopher of science (1902–1994) who defined scientific method through falsifiability and defended liberal democracy in The Open Society and Its Enemies against the totalitarian logic of Plato, Hegel, and Marx.
Popper's philosophy of science established falsifiability as the criterion of genuine science: a theory is scientific only if it makes predictions that could, in principle, be proven wrong. This demarcates science from pseudoscience, astrology, and Freudian psychoanalysis (which, Popper argued, could explain anything and therefore predict nothing).
His political masterwork, The Open Society and Its Enemies (1945), written while fleeing Nazi-occupied Europe, identified the philosophical genealogy of totalitarianism. Plato, Hegel, and Marx all shared a fatal flaw: historicism, the belief that history moves toward a predetermined end that the philosopher has revealed. This belief justifies any atrocity in service of the inevitable future.
The open society, Popper's alternative, is not an end-state but a permanent process: a society that treats its social institutions as fallible human constructs, open to piecemeal criticism and improvement rather than total revolutionary transformation. This is the intellectual foundation of liberal democracy: modest, reformist, anti-utopian.
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What is Popper's open society? ＋
A society that treats its institutions as fallible human constructs open to piecemeal reform, not a utopian end-state but a permanent process of criticism and improvement. The opposite is the closed society, which treats its arrangements as revealed truth.
What is falsifiability? ＋
Popper's criterion for scientific theories: a claim is scientific only if there exists some possible observation that could prove it false. This distinguishes science (which makes testable predictions) from pseudoscience (which can accommodate any outcome).