No True Scotsman

The "No True Scotsman" fallacy is a type of informal logical fallacy that occurs when someone redefines or shifts the criteria of a particular category or group to exclude counterexamples that would otherwise falsify their argument. This fallacy is often used in situations where a person is attempting to protect a cherished belief or claim by making ad hoc adjustments to the definition of a term or group to make their position appear more reasonable.

The name of this fallacy comes from the classic example:

Initial Claim: Person A: "No Scotsman puts sugar on his porridge."

Counterexample: Person B: "But my uncle Angus, who is from Scotland, puts sugar on his porridge."

No True Scotsman Fallacy: Person A (retorts): "Well, no true Scotsman puts sugar on his porridge.

Types and Examples

Religious Belief: Suppose someone argues that "No true Christian would ever commit a crime." When presented with evidence of a Christian who has committed a crime, they respond, "Well, no true Christian would commit such a heinous act."

Political Affiliation: A person might claim, "No real conservative supports government regulations." When confronted with a conservative who supports certain regulations, they might counter with, "That person is not a true conservative."

Dietary Preferences: Someone may assert, "Real vegetarians never eat any animal products." When they learn of a vegetarian who occasionally consumes dairy, they respond, "That's not a true vegetarian."

Fandom and Loyalty: A sports fan might argue, "A true fan always supports the team, win or lose." When another fan criticizes the team's performance, the first fan may say, "You're not a real fan if you criticize the team."

The No True Scotsman fallacy can be used to shield beliefs, ideologies, or groups from criticism or contradictory evidence by redefining the criteria of membership or belief in an ad hoc manner. It's important to be aware of this fallacy in arguments and discussions to ensure that the criteria for a category or group are clear and consistently applied, and to avoid moving the goalposts to protect a particular belief or position.