Karl Popper

Karl Raimund Popper (July 28, 1902 - September 17, 1994), was an Austrian-born, British philosopher of science. He is widely viewed as having been the 20th century's most influential philosopher of science. He was also a social and political philosopher of considerable stature, a staunch defender of liberal democracy and the principles of social criticism upon which it is based, and an implacable opponent of authoritarianism. He is best known for his repudiation of the classical observationalist-inductivist account of science, his espousal of falsifiability as a criterion of demarcation between science and non-science, and his defence of the 'Open Society'.

- Karl Popper -

Born in Vienna in 1902 to middle-class parents of Jewish origins, Karl Popper was educated at the University of Vienna. He took a Ph.D. in philosophy in 1928, and taught in secondary school from 1930 to 1936. In 1937, concerns about the growth of Nazism led him to emigrate to New Zealand, where he became lecturer in philosophy at Canterbury University College, Christchurch. In 1946, he moved to England to become reader in logic and scientific method at the London School of Economics, where he was appointed professor in 1949. He was knighted by Queen Elizabeth II in 1965, and was elected Fellow of the Royal Society in 1976. He retired from academic life in 1969, though he remained intellectually active until his death in 1994. He was invested with the Insignia of a Companion of Honour in 1982.

Popper won many awards and honors in his field, including the Lippincott Award of the American Political Science Association, the Sonning Prize, and fellowships in the Royal Society, British Academy, London School of Economics, Kings College London, and Darwin College Cambridge. Austria awarded him the Grand Decoration of Honour in Gold.

Table of contents
1 Popper's philosophy
2 Critics
3 Bibliography
4 External Links
5 Further reading

Popper's philosophy

Popper coined the term critical rationalism to describe his philosophy. This designation is significant, and indicates his rejection of classical empiricism, and of the observationalist-inductivist account of science that had grown out of it. Popper argued strongly against the latter, holding that scientific theories are universal in nature, and can be tested only indirectly, by references to their implications. He also held that scientific theory, and human knowledge generally, is irreducibly conjectural or hypothetical, and is generated by the creative imagination in order to solve problems that have arisen in specific historico-cultural settings. Logically, no number of positive outcomes at the level of experimental testing can confirm a scientific theory, but a single genuine counter-instance is logically decisive: it shows the theory, from which the implication is derived, to be false. Popper's account of the logical asymmetry between verification and falsification lies at the heart of his philosophy of science. It also inspired him to take falsifiability as his criterion of demarcation between what is and is not genuinely scientific: a theory should be accounted scientific if and only if it is falsifiable. This led him to attack the claims of both psychoanalysis and contemporary Marxism to scientific status, on the basis that the theories enshrined by them are not falsifiable. His scientific work was influenced by his study of Albert Einstein's theory of relativity. Popper's Falsificationism resembles Charles Peirce's falliblism. In Of Clocks and Clouds (1966), Popper said he wished he had known of Peirce's work earlier.

In The Open Society and Its Enemies and The Poverty of Historicism, Popper developed a powerful critique of historicism and a defence of the 'Open Society', liberal democracy. Historicism is the theory that history develops inexorably and necessarily according to knowable general laws towards a determinate end. Popper considered this view to be the principal theoretical presupposition underpinning most forms of authoritarianism and totalitarianism. He accordingly attacked it, arguing that it is founded upon mistaken assumptions regarding the nature of scientific law and prediction. Since the growth of human knowledge is a causal factor in the evolution of human history, and since "no society can predict, scientifically, its own future states of knowledge", it follows, he argued, that there can be no predictive science of human history. For Popper, metaphysical and historical indeterminism go hand in hand.


Some critiques miss the depth of Popper’s insight. For instance, the Quine-Duhem thesis argues that it is impossible to test a single hypothesis on its own, since each one comes as part of an environment of theories. Thus we can only say that the whole package of relevant theories has been collectively falsified, but cannot conclusively say which element of the package must be replaced. An example of this is given by the discovery of the planet Neptune: when the motion of Uranus was found not to match the predictions of Newton's laws, the theory "There are seven planets in the solar system" was rejected, and not Newton's laws themselves. Popper discussed this critique of naďve falsificationism in Chapter 3 & 4 of The Logic of Scientific Discovery. For Popper, theories are accepted or rejected via a sort of 'natural selection'. Theories that say more about the way things appear are to be preferred over those that do not; the more generally applicable a theory is, the greater its value. Thus Newton’s laws, with their wide general application, are to be preferred over the much more specific “the solar system has seven planets”.

Thomas Kuhn’s influential book The Structure of Scientific Revolutions argued that scientists work in a series of paradigms, and found little evidence of scientists actually following a falsificationist methodology. Imre Lakatos, a former student of Popper, attempted to reconcile Kuhn’s work with falsificationism by arguing that science progresses by the falsification of research programs rather than the more specific universal statements of naďve falsificationism. Another of Popper’s students Paul Feyerabend ultimately rejected any prescriptive methodology, replacing method with the aphorism anything goes.

Other critics seek to vindicate the claims of historicism or holism to intellectual respectability, or psychoanalysis or Marxism to scientific status.

One of Popper's students and advocates is the investor George Soros, who says that his investment strategies are based on a Popperian skepticism about the reliability of any human belief. Soros is one of the most successful investors in history.


  • Logik der Forschung, 1934
  • The Open Society and its Enemies, 1946
  • The Logic of Scientific Discovery, 1959
  • The Poverty of Historicism, 1961
  • Conjectures and Refutations: The Growth of Scientific Knowledge, 1963
  • Objective Knowledge: An Evolutionary Approach, 1972
  • Unended Quest; An Intellectual Autobiography, 1976
  • The Self and Its Brain: An Argument for Interactionism, 1977
  • The Open Universe: An Argument for Indeterminism, 1982
  • Realism and the Aim of Science, 1982
  • The Myth of the Framework: In Defence of Science and Rationality, 1994
  • Knowledge and the Mind-Body Problem: In Defence of Interactionism, 1994

Other works and collections:

  • Critical Rationalism: A Re-Statement and Defence by David Miller, 1994
  • Popper Selections (Text by Popper, selected and edited by David Miller)
  • All Life Is Problem Solving (Text by Popper, translation by Patrick Camiller), 1999

External Links

Further reading

  • Feyerabend, P. Against Method. London: New Left Books, 1975. A splendidly polemical, iconoclastic book by a former colleague of Popper's. Vigorously critical of Popper's rationalist view of science.
  • Kuhn, T. S. The Structure of Scientific Revolutions. Chicago: University of Chicago Press, 1962. Central to contemporary philosophy of science is the debate between the followers of Kuhn and Popper on the nature of scientific enquiry. This is the book in which the views of the former received their classical statement.
  • Magee, B. Popper. London: Fontana, 1977. An elegant introductory text. Very readable, albeit rather uncritical of its subject.
  • O'Hear, A. Karl Popper. London: Routledge, 1980. A critical account of Popper's thought, viewed from the perspective of contemporary analytic philosophy.
  • Schilpp, P. A., ed. The Philosophy of Karl Popper, 2 vols. La Salle, IL: Open Court Press, 1974. One of the better contributions to the Library of Living Philosophers series. Contains Popper's intellectual autobiography, a comprehensive range of critical essays, and Popper's responses to them.
  • Stokes, G. Popper: Philosophy, Politics and Scientific Method. Cambridge: Polity Press, 1998. A very comprehensive, balanced study, which focuses largely on the social and political side of Popper's thought.

An earlier version of the above article was posted on 16 May 2001 on Nupedia; reviewed and approved by the Philosophy and Logic group; editor, Wesley Cooper ; lead reviewer, Wesley Cooper ; lead copyeditors, Cindy Seeley and Ruth Ifcher.

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