The Logic of Scientific Discovery
Karl Popper
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In one page
Karl Popper's book — published in German in 1934 and in English in 1959 — is where the site's rule for reading evidence comes from. Popper's target is the idea that science works by piling up confirmations. No number of sightings can prove a universal rule, he argues, while a single contrary observation can break it, and that asymmetry is plain logic: a universal statement is never derivable from singular statements, yet it can be contradicted by one. So he swaps the test. What makes a system scientific is not that you could verify it but that you could refute it — it must be possible, in his words, for an empirical scientific system to be refuted by experience. He is careful that this separates science from non-science rather than sense from nonsense. And he is candid about the cost: science rests on no bedrock, only on piles driven into a swamp until they will carry the structure for now.
Why it matters hereThis is the rule behind chapter 1's evidence ladder and behind the five maturity phrases used on every page of this site: a claim earns its place by naming the measurement that could sink it, and the honest way to hold a bold idea is to say out loud what would overturn it.
What it claims
01Not the verifiability but the falsifiability of a system is to be taken as the criterion of demarcation; a scientific system need not be capable of being singled out once and for all in a positive sense, but it must be possible for an empirical scientific system to be refuted by experience.Section 6, Falsifiability as a Criterion of Demarcation
Settled physics02The proposal rests on an asymmetry between verifiability and falsifiability that follows from the logical form of universal statements: they are never derivable from singular statements but can be contradicted by them, so one may argue deductively, by modus tollens, from the truth of a singular statement to the falsity of a universal one.Section 6
Settled physics03Falsifiability is offered as a criterion of demarcation and not of meaning: it separates two kinds of perfectly meaningful statements, the falsifiable and the non-falsifiable, drawing a line inside meaningful language rather than around it.Section 6, author's note
Settled physics04The game of science is, in principle, without end — whoever decides one day that scientific statements call for no further test, and can be regarded as finally verified, retires from the game.Section 11, Methodological Rules as Conventions
Settled physics05Science does not rest upon solid bedrock: the bold structure of its theories rises above a swamp, like a building erected on piles driven down from above but not to any given base, and when we stop driving them deeper it is not because we have reached firm ground but because we are satisfied they will carry the structure for the time being.Section 30, The Empirical Basis
Settled physics06We do not know, we can only guess — and the marvellously imaginative and bold conjectures we put forward are carefully and soberly controlled by systematic tests; our method of research is not to defend them but to try to overthrow them, using every weapon in the logical, mathematical and technical armoury.Section 85, The Path of Science
Settled physics
The way in
https://archive.org/details/logicofscientifi0000poppFirst published as Logik der Forschung in 1934 and in English by Hutchinson in 1959, in print from Routledge; in copyright, so the site carries the summary and the citation. Scanned copies are lendable through the Internet Archive.
How to cite it
Karl Popper (1959) The Logic of Scientific Discovery. https://archive.org/details/logicofscientifi0000popp
Where it sits in the curriculum