“In so far as a scientific statement speaks about reality, it must be falsifiable; and in so far as it is not falsifiable, it does not speak about reality.”
Karl Popper · Philosophy of science
knowledgemind
Well attested
Philosopher
Last reviewed:
Karl Popper
1902–1994 · Philosophy of science · Modern
Karl Popper argued that science advances by bold conjectures and severe attempts to refute them, not by collecting confirmations. A theory that no possible observation could threaten is, for him, not telling you about the world. The Logic of Scientific Discovery, German in 1934 and English in 1959, states falsifiability as a criterion of demarcation, not of truth.
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A surviving theory is corroborated. It is not verified. Conjectures and Refutations tells the same criterion as an intellectual autobiography, through Einstein, and through Marx, Freud, and Adler as he read them. Whether he is fair to those three is part of the book, not a side issue. The Open Society and Its Enemies is a different project, a defence of piecemeal reform against historicist politics.
Falsifiability does not, by itself, tell you how to vote. He sometimes wrote as if the attitudes were cousins. The cousinship is his hope, not a deduction. He is clearer than the slogan 'science can be wrong', and stricter. Confirmations, he thinks, are cheap.
One two-part sentence was already secured. The demarcation line and the conjectures line are added. A fourth was not padded in. The criterion is one idea said clearly, not a heap of mottoes.
Start here
The first chapter of Conjectures and Refutations, then section 6 of The Logic of Scientific Discovery.
The essay is the argument in public English. The section is the criterion without the autobiography.
Quotations
“Not the verifiability but the falsifiability of a system is to be taken as a criterion of demarcation.”
Karl Popper · Philosophy of science
knowledgemind
Well attested
“The criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.”
Karl Popper · Philosophy of science
knowledgemind
Well attested
Key ideas
Demarcation
Falsifiability, not verifiability, marks an empirical system.
Corroboration
Survival of a hard test is not a proof. It is the most he thinks we get.
Conjecture
Knowledge grows by guesses we try to kill, not by induction piling up yeses.
Open society
Piecemeal reform against theories of history that cannot be wrong.
Major works
The Logic of Scientific Discovery (1934; English 1959)
Section 6 on demarcation.
The Open Society and Its Enemies (1945)
Politics. Not a logic textbook.
Conjectures and Refutations (1963)
The public essay on falsifiability.
Influences
Influenced
- Imre Lakatos
Common misreadings
- Falsifiability does not prove the survivor true. It is a criterion of scientific status.
- A theory that explains every outcome has failed his test, however bold it feels.
- The Open Society is not The Logic of Scientific Discovery. Do not cite one for the other's job.
Famous lines Karl Popper never said
None of the lines this library files for Karl Popper is marked Questionable or Misattributed. That is only a fact about these cards. It is not a certificate that every popular sentence is theirs.
FAQ
What is the best book to start with?
The first chapter of Conjectures and Refutations, then section 6 of The Logic of Scientific Discovery. The essay is the argument in public English. The section is the criterion without the autobiography.
What is the most famous quote?
This library does not measure fame, and it does not rank lines by how often they are shared. The first line it files for Karl Popper that is not marked Questionable or Misattributed is “In so far as a scientific statement speaks about reality, it must be falsifiable; and in so far as it is not falsifiable, it does not speak about reality.” (The Logic of Scientific Discovery, Well attested).
What is the most misquoted line?
None of the lines this library files for Karl Popper is marked Misattributed or Questionable. That is a fact about these cards, not a certificate that every popular sentence is theirs.
What is one key idea, in a sentence?
Demarcation: Falsifiability, not verifiability, marks an empirical system.