No true Scotsman

Philosophy professor Bradley Dowden explains the fallacy as an "ad hoc rescue" of a refuted generalization attempt.[1] The following is a simplified rendition of the fallacy:[6]

The No True Scotsman is committed when the arguer satisfies the following conditions:[7][3][4]

• not publicly retreating from the initial, falsified assertion
• offering a modified assertion that definitionally excludes a targeted unwanted counterexample
• using rhetoric to (un)intentionally hide the modification

An appeal to purity is commonly associated with protecting a preferred group. One can imagine a matter of Scottish national pride is at stake if someone regularly considered to be Scottish commits a heinous crime. Thus, there may be an active interest in protecting members of this shared Scottish heritage from a possible accusation of guilt by association by denying that the group includes this undesirable member or action. “No true 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 counter-example to the group’s good nature. [4]

The description of the fallacy in this form is attributed[8] 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:[4]

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!'

And even earlier in God & Philosophy in 1966;[3]

The Berkeley-Newman contention could be defended only by resort to the No-true-Scotsman Move, and the consequent castration of the thesis. (In this ungracious move a brash generalization, such as No Scotsmen put sugar on their porridge, when faced with falsifying facts, is transformed while you wait into an impotent tautology: if ostensible Scotsmen put sugar on their porridge, then this is by itself sufficient to prove them not true Scotsmen.)

— Antony Flew

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 and mature democracy starts a war against a fellow democracy.[6]

Robert Anderson argues that the phrase "No true Scotsman" is not always fallacious: it depends on the syntactical context of the term "true" inserted into the phrase "no Scotsman".[7]