Definition · Plain-language
No true Scotsman fallacy
The no true Scotsman fallacy is an informal logical fallacy in which a general claim is protected from counterexamples by redefining the category after the fact to exclude them.
The step most authors miss
Doing CRediT right? Don’t stop at the statement.
A CRediT statement credits you inside one paper. The recognition CRediT was built for happens when those roles are tied to you, persistently. Sign in with your ORCID — free — and claim your CRediT contributions on casrai.org, the home of the standard. They become a verified, portable part of your identity, not a line that disappears into one PDF.
Free: claim your contributions, then export a journal-ready CRediT statement, schema.org structured data, JATS XML, CSV or BibTeX — and preview your public profile. A membership publishes that profile publicly and verifies the journals you serve.
Flew’s original example and the structure of the fallacy
Antony Flew named and analysed the fallacy in Thinking About Thinking (1975). His original example: a Scotsman reads about a particularly brutal crime and says, "No Scotsman would do such a thing." When presented with a counterexample — a Scotsman who did commit such a crime — he revises to "No true Scotsman would do such a thing." The revision immunises the generalisation against any possible counterexample by moving the goalposts: the definition of "Scotsman" (or "true Scotsman") is quietly adjusted so that any disconfirming case is excluded by fiat. The claim has become unfalsifiable, but not because it is necessarily true — because it has been redefined to exclude all disconfirmation.
Ad hoc redefinition, falsifiability and special pleading
The fallacy is an instance of ad hoc hypothesis modification — changing a theory only after a refutation to protect it, rather than for principled independent reasons. This violates Karl Popper’s falsifiability criterion: a claim that can be continually redefined to exclude all counterexamples cannot be tested and is therefore not scientifically meaningful. The move also overlaps with special pleading, which claims an exception to a general principle without a principled reason. Circular reasoning is nearby too: the claim that "no true X does Y" defines true X partly by not doing Y, making the generalisation about X trivially true by definition.
Examples in group identity and how to detect the fallacy
The no true Scotsman pattern appears frequently in claims about group identity and ideology. "No true communist would support violence." "No real Christian would vote for that party." "A real scientist would never question this consensus." In each case, when a counterexample is produced, the group boundary is silently redrawn to exclude it. To detect the fallacy, ask: was the definition of X established before or after the counterexample was produced? If the counterexample prompted a new definitional requirement, the move is likely a no true Scotsman. A principled definitional revision with independent justification is different; an ad hoc revision made solely to exclude a particular case is the fallacy.
Key facts
At a glance
- Definition: redefining a category after the fact to exclude counterexamples
- Named by: Antony Flew, Thinking About Thinking (1975)
- Type: informal fallacy of presumption / ad hoc redefinition
- Result: the claim becomes unfalsifiable via shifting goalposts
- Related: special pleading, circular reasoning, ad hoc modification
- Falsifiability link: Popper’s criterion is violated when definitions expand to exclude all cases
- Test: was the definition revised only because the counterexample appeared?
Common misconceptions
What people often get wrong
Often heard: Refining a definition is always a no true Scotsman fallacy.
Actually: The fallacy requires that the redefinition is ad hoc — made only to exclude a particular counterexample with no independent justification. Principled conceptual clarification, where a definition is sharpened for reasons that predate the counterexample, is legitimate philosophical work, not the fallacy.
Often heard: The no true Scotsman fallacy only appears in arguments about nationality.
Actually: Nationality is Flew’s illustrative example, not the scope of the fallacy. It appears in any argument about group membership or generalisation: science, religion, politics, ideology or identity. The structure is: revising who counts as a "true" member to exclude a disconfirming case.
Often heard: If the redefined claim is true, the fallacy doesn’t apply.
Actually: A claim can be true and still be defended via the no true Scotsman fallacy. The fallacy is about the method of defence — immunising a generalisation by ad hoc redefinition — not whether the generalisation happens to be defensible by other means.
Common questions
FAQ
What is the no true Scotsman fallacy in simple terms?+
It is when someone makes a general claim about a group, is presented with a counterexample, and instead of accepting the refutation, moves the goalposts by redefining the group to exclude the counterexample. The word "true" often signals the move: "But no true member of the group would do that."
How is the no true Scotsman fallacy different from circular reasoning?+
They are related but distinct. Circular reasoning assumes the conclusion in the premises. No true Scotsman involves ad hoc redefinition to exclude counterexamples, which can make a claim trivially true by definition — that circularity is a consequence of the redefinition, not its starting point. The primary error is the unprincipled, post-hoc revision of the category.
Can the no true Scotsman fallacy ever be avoided?+
Yes, by establishing clear, principled definitions before examining cases, and by being willing to accept genuine counterexamples as refutations. If a counterexample prompts reconsidering a definition, the revision should be justified on grounds independent of the specific counterexample that triggered it.
Going deeper
