No True Scotsman

The no true Scotsman fallacy occurs when a universal claim is defended by excluding counterexamples based on a biased definition. This tactic allows the speaker to maintain their argument by shifting the criteria for what qualifies as a member of a group.

For instance, if someone claims that 'no Scotsman puts sugar in his porridge,' and when presented with a Scotsman who does, they respond that 'no true Scotsman would do that,' they are committing this fallacy. It is essential to define terms clearly and fairly to foster honest debate.