Karl Popper
A theory is scientific only if it could be refuted by observation, and a free society lives by criticism, not by grand plans for history.
Placement
Critical rationalism: theories are not verifiable but falsifiable; the open society against historicism.
Key ideas
- Falsification
- Open society
- Critical rationalism
Students: Paul Feyerabend
Influence
Influenced by 5
Socrates
influenced by ✓
Popper took Socrates’ awareness of his ignorance and his critical questioning as the model of critical rationalism, set against Plato’s ‘spell’ (The Open Society and Its Enemies, 1945). K. R. Popper, The Open Society and Its Enemies, vol. I: The Spell of Plato (1945); SEP “Karl Popper”
Socrates › 470–399 BCE
David Hume
influenced by
Popper accepted Hume’s argument that induction cannot be logically justified but rejected his psychology of habit, replacing induction with conjecture and falsification (Objective Knowledge, 1972). K. R. Popper, Logik der Forschung (1934); Objective Knowledge (1972), “Conjectural Knowledge: My Solution of the Problem of Induction”; SEP “Karl Popper”
Evidence: also in InPhO · InPhO
David Hume › 1711–1776
Immanuel Kant
influenced by
Popper called demarcation ‘Kant’s problem’ and reinterpreted Kant’s claim that the intellect prescribes its laws to nature: we propose conjectures, which nature may defeat (Conjectures and Refutations, 1963). K. R. Popper, Logik der Forschung (1934); “Kant’s Critique and Cosmology” (1954), in Conjectures and Refutations (1963); SEP “Karl Popper”
Evidence: also in InPhO · InPhO
Immanuel Kant › 1724–1804
Albert Einstein
influenced by ✓
Popper drew his falsifiability criterion from Einstein’s risky prediction of light deflection, tested in 1919, in contrast to Marx, Freud and Adler (Conjectures and Refutations, 1963). K. R. Popper, “Science: Conjectures and Refutations” (lecture 1953), in Conjectures and Refutations (1963); Unended Quest (1976); SEP “Karl Popper”
Albert Einstein › 1879–1955
Alfred Tarski
influenced by
Popper credited Tarski, who explained his theory to him in Vienna (1935), with rehabilitating correspondence truth, and built on it his notion of verisimilitude (Conjectures and Refutations, 1963). K. R. Popper, Conjectures and Refutations (1963); Objective Knowledge (1972); Unended Quest (1976); SEP “Karl Popper”
Evidence: also in InPhO · InPhO
Alfred Tarski › 1901–1983
Influenced 1
Abdolkarim Soroush
influenced
Soroush took up Popper’s fallibilism for his theory that religious knowledge, unlike religion itself, is human, historical and revisable (The Contraction and Expansion of Religious Knowledge, 1990). A. Soroush, Qabz va bast-e teorik-e shariat (1990); M. Sadri & A. Sadri (eds.), Reason, Freedom, and Democracy in Islam (2000)
Evidence: also in InPhO · InPhO
Abdolkarim Soroush › b. 1945
Criticism
Criticized by 5
Theodor W. Adorno
criticised by
In the positivism dispute Adorno objected that Popper’s critical rationalism confines criticism to testing hypotheses rather than to society as a contradictory totality (Tübingen, 1961; Der Positivismusstreit, 1969). T. W. Adorno, “Zur Logik der Sozialwissenschaften” (reply to K. Popper, Tübingen 1961), in Der Positivismusstreit in der deutschen Soziologie (1969)
Evidence: AI draft
Theodor W. Adorno › 1903–1969
Thomas S. Kuhn
criticised by
Kuhn objected to Popper that normal science solves puzzles without testing its paradigm, which single anomalies do not overturn (‘Logic of Discovery or Psychology of Research?’, 1970). T. S. Kuhn, “Logic of Discovery or Psychology of Research?”, in I. Lakatos & A. Musgrave (eds.), Criticism and the Growth of Knowledge (1970); Popper’s reply “Normal Science and Its Dangers”, ibid.
Evidence: AI draft
Thomas S. Kuhn › 1922–1996
Imre Lakatos influenced
influenced ✓
Lakatos, Popper’s colleague at the LSE from 1960, applied his critical rationalism to mathematics, whose growth he traced through proofs and counterexamples (‘Proofs and Refutations’, 1963–64). I. Lakatos, “Proofs and Refutations”, British Journal for the Philosophy of Science 14 (1963–64); SEP “Imre Lakatos”
criticised by
Against Popper’s naive falsificationism, Lakatos argued that single refutations decide nothing; research programmes are judged as progressive or degenerating (‘Falsification and the Methodology of Scientific Research Programmes’, 1970). I. Lakatos, “Falsification and the Methodology of Scientific Research Programmes” (1970); “Popper on Demarcation and Induction”, in P. A. Schilpp (ed.), The Philosophy of Karl Popper (1974)
Evidence: AI draft
Imre Lakatos › 1922–1974
Paul Feyerabend taught
taught ✓
Feyerabend came to the London School of Economics in 1952–53 on a British Council scholarship to study with Popper – he had hoped to work with Wittgenstein, who died in 1951 – and defended Popper’s views for some years before turning against them. P. Feyerabend, Killing Time (1995)
Evidence: also in Wikidata · Wikidata
criticised by
Feyerabend argued that Popper’s falsificationism, applied strictly, would have wiped out science, since every theory conflicts with some known facts (Against Method, 1975, ch. 5). P. Feyerabend, Against Method (1975), ch. 5; “Consolations for the Specialist”, in I. Lakatos & A. Musgrave (eds.), Criticism and the Growth of Knowledge (1970)
Evidence: AI draft
Paul Feyerabend › 1924–1994
Jürgen Habermas
criticised by
Habermas attacked Popper’s critical rationalism as a ‘positivistically halved rationalism’ that confines reason to method and leaves the choice of values to decision (1963–64, in Der Positivismusstreit, 1969). J. Habermas, “Analytische Wissenschaftstheorie und Dialektik” (1963); “Gegen einen positivistisch halbierten Rationalismus” (1964, reply to H. Albert); both in Der Positivismusstreit in der deutschen Soziologie (1969)
Evidence: AI draft
Jürgen Habermas › 1929–2026
Criticizes 9
Plato
criticised
Popper read Plato’s ideal state as a closed society and his historicism and holism as an intellectual source of modern totalitarianism (The Spell of Plato, 1945). K. Popper, The Open Society and Its Enemies, vol. 1: The Spell of Plato (1945); critique: R. B. Levinson, In Defense of Plato (1953)
Evidence: AI draft
Plato › 428–348 BCE
Aristotle
criticised
Popper attacked Aristotle’s ‘methodological essentialism’, the search for definitions of essences, as a root of Hegelian historicism (The Open Society and Its Enemies, 1945). K. R. Popper, The Open Society and Its Enemies, vol. 2 (1945), ch. 11 (“The Aristotelian Roots of Hegelianism”)
Evidence: AI draft
Aristotle › 384–322 BCE
Georg Wilhelm Friedrich Hegel
criticised
Popper read Hegel as a historicist apologist of the Prussian state whose dialectic prepared modern totalitarianism (The Open Society and Its Enemies, 1945, vol. 2, ch. 12). K. Popper, The Open Society and Its Enemies (1945), vol. 2, ch. 12 “Hegel and the New Tribalism”; critique of this reading: W. Kaufmann, “The Hegel Myth and Its Method”, Philosophical Review 60 (1951)
Evidence: AI draft
Georg Wilhelm Friedrich Hegel › 1770–1831
Karl Marx
criticised
Popper argued that Marx’s historicism claims to predict history; when its prophecies failed, they were reinterpreted, making the theory immune to criticism (The Open Society, 1945). K. Popper, The Open Society and Its Enemies (1945), vol. 2; Conjectures and Refutations (1963), ch. 1; The Poverty of Historicism (1957)
Evidence: AI draft
Karl Marx › 1818–1883
Sigmund Freud
criticised
Popper argued that psychoanalysis can interpret any behaviour in its own terms; its constant confirmations show that it cannot be tested (Conjectures and Refutations, 1963, ch. 1). K. Popper, Conjectures and Refutations (1963), ch. 1 “Science: Conjectures and Refutations”
Evidence: AI draft
Sigmund Freud › 1856–1939
Ludwig Wittgenstein
criticised
Popper rejected Wittgenstein’s view that there are no genuine philosophical problems, and objected that the Tractatus’ criterion of meaning would also exclude natural laws (Logik der Forschung, 1934). K. Popper, Logik der Forschung (1934), §§ 4, 10; “The Nature of Philosophical Problems and Their Roots in Science” (1952), in Conjectures and Refutations (1963)
Evidence: AI draft
Ludwig Wittgenstein › 1889–1951
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Otto Neurath
criticised
Popper welcomed Neurath’s view that protocol sentences are revisable, but objected that without rules for discarding them empiricism is thrown overboard (Logik der Forschung, 1934). K. Popper, Logik der Forschung (1934), § 26; O. Neurath, “Protokollsätze”, Erkenntnis 3 (1932/33)
Evidence: AI draft
Otto Neurath › 1882–1945
Rudolf Carnap
criticised
Popper rejected Carnap’s verifiability criterion of meaning and inductive logic, proposing falsifiability as a criterion of demarcation, not of meaning (‘The Demarcation between Science and Metaphysics’, 1963). K. Popper, Logik der Forschung (1934), §§ 4–6; “The Demarcation between Science and Metaphysics”, in P. A. Schilpp (ed.), The Philosophy of Rudolf Carnap (1963), with Carnap’s reply
Evidence: AI draft
Rudolf Carnap › 1891–1970
Hans Reichenbach
criticised
Popper rejected Reichenbach’s probability logic of induction: no principle of induction can be justified without infinite regress, and hypotheses cannot be assigned probabilities (Logik der Forschung, 1934). K. Popper, Logik der Forschung (1934), §§ 1, 80–81; H. Reichenbach, Wahrscheinlichkeitslehre (1935)
Evidence: AI draft
Hans Reichenbach › 1891–1953
Works
Falsifiability instead of verification – a solution to the problem of induction?
Against Plato, Hegel and Marx: historicism threatens freedom.
Position
Popper started from Hume’s problem of induction: no number of observed white swans proves that all swans are white. Science therefore cannot verify its theories – but it can refute them. A theory is scientific if it forbids something and thus risks being falsified; theories that explain everything, like certain forms of Marxism or psychoanalysis in his view, explain nothing. Knowledge grows through bold conjectures and rigorous attempts at refutation. Popper carried this critical rationalism into politics: against Plato, Hegel and Marx he defended the “open society,” in which institutions can be corrected without bloodshed and no one claims to know the course of history. His ideas influenced scientists and politicians far beyond philosophy.
Life & context
Popper was born in Vienna in 1902, worked as a teacher and took his doctorate in 1928 with a thesis on the method of the psychology of thought; he stood close to the Vienna Circle without belonging to it. In 1937 he fled the rise of National Socialism to New Zealand, where he wrote The Open Society. From 1946 he taught at the London School of Economics; he was knighted in 1965 and died in London in 1994.
Further main works
- The Poverty of Historicism (1957)
- Conjectures and Refutations (1963)
- Objective Knowledge (1972)
Appears in
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