Karl Popper

Key ideas

Popper accepted David Hume's argument that induction cannot be justified, and concluded that science does not rely on it. Scientists propose bold conjectures and then try to refute them. No number of observations can prove a theory true, but a single clear counterexample can show it false. What marks a theory as scientific is falsifiability.

He used this criterion to contrast Einstein's relativity, which made risky predictions that could have failed, with theories such as psychoanalysis and some forms of Marxism, which he thought could explain any outcome and so explained nothing. His ideas are central to science and truth and to responses to the problem of induction.

In politics he defended the 'open society', in which policies are treated as conjectures to be tested and corrected, against all-encompassing utopian plans.

Life, briefly

Popper grew up in Vienna and trained as a teacher before publishing his first major book in 1934. He left Austria in 1937, ahead of the Nazi annexation, and taught in New Zealand during the war. From 1946 he taught at the London School of Economics. He was knighted in 1965.

Major works

• The Logic of Scientific Discovery (German 1934, English 1959)
• The Open Society and Its Enemies (1945)
• Conjectures and Refutations (1963)

Further reading

• EncyclopediaStanford Encyclopedia of Philosophy: Karl Popper
• WikipediaKarl Popper