Thomas Kuhn and Karl Popper are the two most influential philosophers of science of the 20th century, and they disagreed about almost everything fundamental. Popper argued science advances by bold conjectures and ruthless attempts at falsification — science is distinguished from pseudo-science by its falsifiability. Kuhn argued this bears no resemblance to how science actually works — scientists work within paradigms, protect their core assumptions, and only revolution (not refutation) changes fundamental science.
| Category | Thomas Kuhn | Karl Popper |
|---|---|---|
| Born | 1922, Cincinnati, Ohio, USA | 1902, Vienna, Austria |
| Died | 1996, Cambridge, Massachusetts | 1994, London, England |
| Core claim | Science advances through paradigm shifts — revolutionary episodes replacing one framework with another; normal science is puzzle-solving within paradigms | Science advances through falsification — bold conjectures tested against reality; unfalsifiable claims are not science |
| What distinguishes science? | The existence of a shared paradigm (orits absence in pre-paradigm stage) — not falsifiability | Falsifiability: a theory is scientific only if it makes predictions that could in principle be false |
| On Freud and Marx | Probably classifiable as science if there's a paradigm — Kuhn doesn't rely on falsifiability | Pseudo-science — not falsifiable; any observation can be explained away |
| Normal science | Scientists don't try to overthrow their paradigm — they work within it; anomalies are ignored until they accumulate beyond tolerance | Scientists should always try to falsify; failure to do so is a failure of scientific virtue |
| Examples of revolution | Copernican revolution, chemical revolution (Lavoisier), relativity — not just accumulation of evidence | Revolution comes when experiments falsify predictions — but Kuhn showed scientists resist this |
Kuhn more accurately describes how science actually works historically. Popper more accurately describes how science should work normatively. Both are right in their domain: Popper for scientific virtue, Kuhn for scientific sociology.
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