No True Scotsman

The No True Scotsman Fallacy is a form of informal logical fallacy in which someone attempts to protect a universal generalization from a counterexample by changing or narrowing the definition of the group in question. Rather than accepting that their original claim was too broad, the person redefines the category to exclude the inconvenient example. The fallacy was identified and named by philosopher Antony Flew in 1975, who illustrated it with the following scenario: A Scotsman reads about a crime in the newspaper and declares, "No Scotsman would do such a thing." When shown that the perpetrator was indeed Scottish, rather than accepting this counterexample, he responds, "Well, no true Scotsman would do such a thing."

The core problem with this fallacy is the ad hoc redefinition of terms. The original claim is presented as applying to all members of a group. When a counterexample is raised, the speaker retroactively narrows the definition of the group to exclude the counterexample, effectively making the claim unfalsifiable. This is logically invalid because the revised definition has no independent justification—it exists solely to protect the original generalization.

The No True Scotsman Fallacy is common in everyday debates and discussions, particularly when people are defending idealized views of groups they identify with. For example, members of a political party might claim that no one in their party supports a controversial policy, and when shown a member who does, they respond that the person is not a "true" member of the party. Recognizing this fallacy is important for constructive discourse: when a counterexample challenges a universal claim, the honest response is to revise the claim rather than redefine the group.