No true Scotsman

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.<ref name="iep">Template:Cite web</ref><ref name=FallacyFilesWebsite>Template:Cite web</ref><ref name=godandphilo>Template:Cite book</ref> 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.<ref name="Flew1975" /><ref name=FallacyFilesWebsite/>

Philosopher Bradley Dowden explains the fallacy as an "ad hoc rescue" of a refuted generalization attempt.<ref name="iep"/> The following is a simplified rendition of the fallacy:<ref name="atimes"/>

<poem style="margin-left: 2em;"> 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 Template:Em Scotsman puts sugar on his porridge."</poem>

Occurrence

The "no true Scotsman" fallacy is committed when the arguer satisfies the following conditions:<ref name=godandphilo/><ref name=Flew1975/><ref name="anderson">Template:Cite conference</ref>

• 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 Template:Em 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.<ref name=Flew1975>Template:Cite book</ref>

Origin and philosophy

The description of the fallacy in this form is attributed to the British philosopher Antony Flew, who wrote, in his 1966 book God & Philosophy,

In his 1975 book Thinking About Thinking, Flew wrote:<ref name="Flew1975" />

Template:Blockquote 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 Template:Em democracy starts a war against a fellow democracy.<ref name="atimes">Template:Cite web</ref>

Cognitive psychologist Steven Pinker has suggested that phrases like "no true Christian ever kills, no true communist state is repressive and no true Trump supporter endorses violence" exemplify the fallacy.<ref>Template:Cite book</ref>

See also

• Ad hoc hypothesis
• Begging the question
• Epistemic commitment
• Equivocation
• List of fallacies
• Moving the goalposts
• Persuasive definition
• Reification (fallacy)
• Special pleading
• Whataboutism