Philosophy

Karl Popper

1902–1994 · Austrian-British

Philosophy of science; critical rationalism; liberalism

Sir Karl Popper was a Vienna-born philosopher of science and political philosopher who spent most of his career at the London School of Economics. He rejected inductive verification and argued that the mark of a scientific theory is falsifiability, so that science advances through bold conjectures and attempted refutations. In The Open Society and Its Enemies he defended liberal democracy against the historicism he found in Plato, Hegel and Marx.

How to spot them

▸Falsifiability / falsificationism; the demarcation problem; conjectures and refutations
▸Critical rationalism; black swans; Einstein vs Freud, Adler and Marx as pseudo-science
▸The Open Society and Its Enemies; historicism; the paradox of tolerance; piecemeal social engineering
▸LSE; Logik der Forschung; the poker incident with Wittgenstein

Key works

The Logic of Scientific Discovery (1959)

English version of Logik der Forschung (1934): falsifiability as the criterion of demarcation for science

The Open Society and Its Enemies (1945)

Written in New Zealand; attacks Plato, Hegel and Marx as enemies of the open, liberal society

The Poverty of Historicism (1957)

Argues history has no predictable laws of development; first published as articles in 1944–45

Conjectures and Refutations (1963)

Essays arguing that knowledge grows by bold guesses and their critical testing

Objective Knowledge (1972)

"An Evolutionary Approach"; introduces his theory of three worlds (physical, mental, and objective contents of thought)

Key ideas

Problem of induction: no number of confirming observations can prove a universal theory (seeing white swans cannot prove all swans are white), but one counter-instance can refute it
Falsifiability as the criterion of demarcation: a theory is scientific only if it makes claims that observation could show to be false
Marxism, Freudian psychoanalysis and Adler's individual psychology were criticised as pseudo-scientific because they could accommodate any evidence, unlike Einstein's risky predictions
Critical rationalism: knowledge grows through conjectures and refutations, not certainty, and all knowledge remains fallible
Historicism, the belief in inexorable laws of historical development, is false and underpins totalitarian utopianism; reform should proceed by piecemeal social engineering
Paradox of tolerance: unlimited tolerance can lead to the disappearance of tolerance, so a tolerant society may need to refuse tolerance to the intolerant

Quick-fire facts

•Born in Vienna to a family of Jewish origin; associated with, but a critic of, the Vienna Circle
•Logik der Forschung was published in Vienna in late 1934 (dated 1935)
•Fled the rise of Nazism in 1937 to teach at Canterbury University College, Christchurch, New Zealand, where he wrote The Open Society
•Taught at the London School of Economics from 1946, becoming Professor of Logic and Scientific Method
•Knighted in 1965 and made a Companion of Honour in 1982
•Clashed with Ludwig Wittgenstein at the Cambridge Moral Sciences Club in 1946 in the "poker incident"
•His ideas influenced George Soros, whose Open Society Foundations are named after Popper's book

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Sources

Stanford Encyclopedia of Philosophy — Karl Popper
Anthony Kenny — A New History of Western Philosophy