Karl Popper 1902 – 1994

Karl Popper was a 20th-century Austrian-British philosopher of science, social philosopher, and one of the most influential thinkers of the analytic tradition. The Logic of Scientific Discovery, originally published in German in 1934, argued that scientific theories cannot be verified but can be falsified, and that falsifiability is the criterion that distinguishes empirical science from non-science. The Open Society and Its Enemies, written during the Second World War, defended liberal democracy and analytical critique against the historicism he found in Plato, Hegel, and Marx. He also articulated the paradox of tolerance, the principle that an open society must be intolerant of intolerance to survive. Knighted in 1965, he taught for most of his career at the London School of Economics.

Karl Popper (1902–1994) was born in Vienna to a Jewish family that had converted to Lutheranism, taught philosophy at Canterbury University College in New Zealand from 1937 (escaping Nazi Europe), and held the chair in logic and scientific method at the London School of Economics from 1946 until his retirement.

The Logic of Scientific Discovery (1934, English translation 1959) is Popper's most influential work in the philosophy of science. It argues against the verificationism of the Vienna Circle that no finite set of confirming observations can establish a scientific theory, and that the proper criterion of demarcation between science and pseudo-science is falsifiability: a theory is scientific if it forbids observable states of affairs and is therefore in principle refutable.

The Open Society and Its Enemies (1945) and The Poverty of Historicism (1957) extend Popper's critical-rationalist framework to political philosophy. The Open Society attacks Plato, Hegel, and Marx as the philosophical sources of twentieth-century totalitarianism and defends piecemeal social engineering against utopian and revolutionary alternatives. Popper's later work on objective knowledge, the three worlds ontology, and evolutionary epistemology rounds out a body of work that has shaped the philosophy of science, political philosophy, and the broader self-understanding of liberal democracy.