No true Scotsman
No true Scotsman or appeal to purity is an informal fallacy in which one attempts to protect a universal generalization from counterexamples by changing the definition in an ad hoc fashion to exclude the counterexample. Rather than denying the counterexample or rejecting the original claim, this fallacy modifies the subject of the assertion to exclude the specific case or others like it by rhetoric, without reference to any specific objective rule ("no true Scotsman would do such a thing"; i.e., those who perform that action are not part of our group and thus criticism of that action is not criticism of the group).
Person A: "No Scotsman puts sugar on his porridge."
Person B: "But my uncle Angus is a Scotsman and he puts sugar on his porridge."
Person A: "But no true Scotsman puts sugar on his porridge."
The essayist David P. Goldman, writing under his pseudonym "Spengler" compared distinguishing between "mature" democracies, which never start wars, and "emerging democracies", which may start them, with the "No true Scotsman" fallacy. Spengler alleges that political scientists have attempted to save the "US academic dogma" that democracies never start wars from counterexamples by declaring any democracy which does indeed start a war to be flawed, thus maintaining that no true democracy starts a war.
The introduction of the term is attributed to British philosopher Antony Flew, because the term originally appeared in Flew's 1971 book An Introduction to Western Philosophy. In his 1975 book Thinking About Thinking, he wrote:
Imagine Hamish McDonald, a Scotsman, sitting down with his Glasgow Morning Herald and seeing an article about how the "Brighton Sex Maniac Strikes Again". Hamish is shocked and declares that "No Scotsman would do such a thing." The next day he sits down to read his Glasgow Morning Herald again; and, this time, finds an article about an Aberdeen man whose brutal actions make the Brighton sex maniac seem almost gentlemanly. This fact shows that Hamish was wrong in his opinion, but is he going to admit this? Not likely. This time he says: "No true Scotsman would do such a thing."
- Ad hoc rescue
- Begging the question
- Epistemic commitment
- List of fallacies
- Loaded language
- Moving the goalposts
- Persuasive definition
- Reification (fallacy)
- Special pleading
- Tautology (rhetoric)
- No True Scotsman, Internet Encyclopedia of Philosophy
- Curtis, Gary N. "Redefinition". Fallacy Files. Retrieved 2016-11-12.
- Flew, Antony (1975), Thinking About Thinking: Do I Sincerely Want to Be Right?, London: Collins Fontana, p. 47, ISBN 978-0-00-633580-1
- Goldman, David P. (31 Jan 2006). "No true Scotsman starts a war". Asia Times. Retrieved 1 December 2014.
political-science professors... Jack Mansfield and Ed Snyder distinguish between "mature democracies", which never, never start wars ("hardly ever", as the captain of the Pinafore sang), and "emerging democracies", which start them all the time, in fact far more frequently than do dictatorships
- "Obituary: Prof. Antony Flew", The Scotsman, 16 April 2010