No true Scotsman is a term coined by Antony Flew in his 1975 book Thinking About Thinking – or do I sincerely want to be right?^[1]:

Imagine Hamish McDonald, a Scotsman, sitting down with his Press and Journal 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 Press and Journal 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."

Flew's original example may be softened into the following :

Argument: "No Scotsman puts sugar on his porridge."

Reply: "But my uncle Angus, who is a Scotsman, likes sugar with his porridge."

Rebuttal: "Aye, but no true Scotsman puts sugar on his porridge."

This form of argument is an informal fallacy if the predicate ("putting sugar on porridge" or "doing such a thing [as committing a sex crime]") is not actually contradictory for the accepted definition of the subject ("Scotsman"), or if the definition of the subject is silently adjusted after the fact to make the rebuttal work.^[2]

Source of the fallacy

The truth of a proposition depends on its adequacy to its object ("Is the drawing a true likeness of Antony Flew?"). The truth of an object depends on its adequacy to its concept ("Is the figure drawn on the paper a true triangle?"). Problems arise when the definition of the concept has no generally accepted form, for example when it is vague or contested.

"A true Scotsman" (a concept) is not on the same level as "a true triangle" (a concept) never mind "the true Antony Flew" (a concrete existing object). The formal similarity, "true X", and the corresponding feeling that the concepts should be on the same level, in some sense must be on the same level (even perhaps all exist as objects), motivates the fallacy. It is a short step from that feeling to treating one's own definition of a "true Scotsman" (who else's?) as having the same objectivity as that of a geometrical figure or an existing individual, and then attempting to make the world agree.

Examples

This fallacious technique is often used in politics, in which critics may condemn their colleagues as not being "true" Communists, liberals, conservatives, etc. because of a disagreement concerning certain matters of policy. For example, it may be argued that "No decent person would support hanging", "watch pornography", or "smoke in public". Often the speaker seems unaware that he is, in fact, coercively (re)defining the meaning of the phrase "decent person" to gain tactical advantage in the argument. The use of this technique shifts the debate away from the merits of hanging, pornography, or smoking (or whatever controversial subject that may be at issue) by attempting to establish, without basis in logic, that anyone disagreeing with the speaker is, in fact, "indecent".

Exceptions

Some elements or actions are clearly contradictory to the subject, and therefore aren't fallacies. The statement "No true Scotsman would be born and raised in India to Indian parents" is not fallacious because it follows from the accepted definition of "Scotsman", which is having significant cultural or genealogical relation to Scotland. We might argue about the degree to which one must have that relation to be a "true" Scotsman (the fallacy); however there can be no dispute that zero relation actually does disqualify. The statement "No true vegetarian would eat a beef steak" is not fallacious because it follows from the accepted definition of "vegetarian": Eating meat, by definition (rather than just by association), disqualifies a (present-tense) categorization among vegetarians, and the further value judgement between a "true vegetarian" and the implied "false vegetarian" cannot likewise be categorized as a fallacy, given the clear disjunction. However, the "no true Scotsman" fallacy might also be used in claiming that no "true" vegetarian would wear fur or leather, as this hinges on a (possible) associated trait, rather than the definition of vegetarianism.

Alternatively, if a statement in the "no true Scotsman" form is not intended as an empirical argument, but as the conclusion to an argument about definition, then it is not a fallacy. It is possible to make formally valid arguments about contested definitions. The statement "No true Marxist would support the Soviet invasion of Hungary because the basic goal of Marxism is the self-emancipation of the working class" may or may not be true, but it is not an instance of the "no true Scotsman" fallacy.

See also

• Equivocation
• Euphemism
• Loaded language
• Power word
• Reification (fallacy)

External links

• WWW source of the quote at the top of the page.

References

•  • [ e] Informal fallacies
Special pleading • Red herring • Gambler's fallacy and its inverse • Fallacy of distribution (Composition • Division) • Begging the question • Many questions
Correlative-based fallacies:	False dilemma (Perfect solution) • Denying the correlative • Suppressed correlative
Deductive fallacies:	Accident • Converse accident
Inductive fallacies:	Hasty generalization • Overwhelming exception • Biased sample • False analogy • Misleading vividness • Conjunction fallacy
Vagueness and Ambiguity:	False precision • Slippery slope • Continuum fallacy
Equivocation:	Equivocation • False attribution • Fallacy of quoting out of context • Loki's Wager • No true Scotsman
Questionable cause:	Correlation does not imply causation (Cum hoc) • Post hoc • Regression fallacy • Texas sharpshooter • Circular cause and consequence • Wrong direction • Single cause