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Karl Popper (1902–1994)

Popper made fallibilism central to the philosophy of science. His conjecture and refutation — knowledge grows through error-elimination, never arriving at final truth — insisted that no vocabulary is final and no description is complete. His open society — institutions treated as conjectures, open to criticism — applied the same principle to politics. But Popper sought a universal demarcation criterion, one rule to separate science from non-science. Kuhn and Feyerabend moved past him in directions SPLectrum follows: no single rule holds across all contexts.

Karl Popper (1902–1994). Philosopher of science who replaced verification with falsification. Born in Vienna, he wrote The Logic of Scientific Discovery in dialogue with the Vienna Circle’s logical positivism — close to them but rejecting their verification principle. He fled Austria in 1937 (Jewish ancestry), spent the war years in New Zealand (Canterbury University College), then moved to the London School of Economics in 1946 where he spent the rest of his career. Knighted in 1965. His students — Lakatos, Feyerabend, Agassi — each moved away from his programme in different directions. A theory is scientific not because it can be confirmed but because it can, in principle, be refuted. Science advances not by accumulating truths but by eliminating errors — bold conjectures subjected to severe tests, surviving until they fail.

Key concepts

Falsificationism. The demarcation criterion: what distinguishes science from non-science is not verifiability but falsifiability. A theory that cannot be refuted by any conceivable observation is not scientific. The stronger the theory — the more it risks — the more scientific it is. The Duhem-Quine objection — that you can never falsify a single hypothesis in isolation because any test relies on auxiliary assumptions — is the best-known challenge. Popper acknowledged it but argued that methodological conventions can handle it. The objection motivated Lakatos’s research programmes and Kuhn’s paradigms — both partly responses to Popper.

Conjecture and refutation. Science does not start from observation and generalise. It starts from problems, proposes bold conjectures, and then tries to refute them. What survives refutation is provisionally accepted — never confirmed, only not yet falsified. Knowledge grows through error-elimination.

The open society. In The Open Society and Its Enemies, Popper extends falsificationism to politics. A society that treats its institutions as conjectures — open to criticism and reform — is an open society. A society that claims to have found the final truth and organises itself around it is closed. Plato, Hegel, and Marx are his targets — though his readings of all three, especially Hegel, have been widely contested.

Three worlds. World 1 is physical reality. World 2 is subjective experience. World 3 is the world of objective knowledge — theories, problems, arguments — that exists independently of any individual mind. A published theorem belongs to World 3 even if everyone who understands it dies. Knowledge is a product that outlives its producers.

Verisimilitude. Popper’s attempt to capture the intuition that science gets closer to truth without ever arriving. A theory has greater verisimilitude than another if it has more truth-content and less falsity-content. The concept proved technically problematic but the intuition remains: not truth but increasing approximation.

Where Popper stops

Popper’s fallibilism is powerful — but it assumes a single game. Falsification works within a paradigm; across paradigms, as Kuhn showed, the rules change. Popper’s demarcation criterion seeks a universal boundary between science and non-science; Feyerabend showed that history consistently violates it. And World 3 — objective knowledge independent of knowers — reintroduces the outside view through the back door: knowledge as a thing out there, detached from the subjects who constitute it. The SPLectrum seed says the opposite: knowledge is constituted through shared language, lives in the relational space between subjects, and has no existence apart from the communities that sustain it.

Key works

The Logic of Scientific Discovery (1934) — falsificationism, the demarcation problem
The Open Society and Its Enemies (1945) — against historicism and utopian politics
The Poverty of Historicism (1957) — against the idea that history has discoverable laws
Conjectures and Refutations (1963) — the growth of knowledge through error-elimination
Objective Knowledge (1972) — epistemology without a knowing subject, World 3