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).
Philosophy professor Bradley Dowden explains the fallacy as an "ad hoc rescue" of a refuted generalization attempt. The following is a simplified rendition of the fallacy:
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 against other democracies from counterexamples by declaring any democracy which does indeed start a war against another democracy to be flawed, thus maintaining that no true democracy starts a war against a fellow democracy.
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 some Scottish chauvinist settled down one Sunday morning with his customary copy of The News of the World. He reads the story under the headline, 'Sidcup Sex Maniac Strikes Again'. Our reader is, as he confidently expected, agreeably shocked: 'No Scot would do such a thing!' Yet the very next Sunday he finds in that same favourite source a report of the even more scandalous on-goings of Mr Angus McSporran in Aberdeen. This clearly constitutes a counter example, which definitively falsifies the universal proposition originally put forward. ('Falsifies' here is, of course, simply the opposite of 'verifies'; and it therefore means 'shows to be false'.) Allowing that this is indeed such a counter example, he ought to withdraw; retreating perhaps to a rather weaker claim about most or some. But even an imaginary Scot is, like the rest of us, human; and none of us always does what we ought to do. So what he is in fact saying is: 'No true Scotsman would do such a thing!'
- No True Scotsman, Internet Encyclopedia of Philosophy
- Curtis, Gary N. "Redefinition". Fallacy Files. Retrieved 2016-11-12.
- Antony Flew (1975). Thinking About Thinking (or, Do I Sincerely Want to be Right?). Fontana/Collins. p. 47.
- 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