No true Scotsman, or appeal to purity, is an informal fallacy in which one modifies a prior claim in response to a counterexample by asserting the counterexample is excluded by definition. Rather than admitting error or providing evidence to disprove the counterexample, the original claim is changed by using a non-substantive modifier such as "true", "pure", "genuine", "authentic", "real", or other similar terms.
- not publicly retreating from the initial, falsified a posteriori assertion
- offering a modified assertion that definitionally excludes a targeted unwanted counterexample
- using rhetoric to signal the modification
An appeal to purity is commonly associated with protecting a preferred group. Scottish national pride may be at stake if someone regularly considered to be Scottish commits a heinous crime. To protect people of Scottish heritage from a possible accusation of guilt by association, one may use this fallacy to deny that the group is associated with this undesirable member or action. "No Scotsman would do something so undesirable"; i.e., the people who would do such a thing are tautologically (definitionally) excluded from being part of our group such that they cannot serve as a counterexample to the group's good nature.
Origin and philosophy
The description of the fallacy in this form is attributed to the English philosopher Antony Flew, who wrote, in his 1966 book God & Philosophy,
In his 1975 book Thinking About Thinking, Flew wrote:
See also
- Ad hoc hypothesis
- Begging the question
- Epistemic commitment
- Equivocation
- List of fallacies
- Motte-and-bailey fallacy
- Moving the goalposts
- Persuasive definition
- Reification (fallacy)
- Special pleading
- Whataboutism