No True Scotsman
Also known as: appeal to purity
Rescuing a generalization from a counterexample by redefining the group on the spot: no *real* X would do that.
Examples
Philosopher Antony Flew told the original version of this story: someone claims “no Scotsman puts sugar on his porridge.” Told about a Scotsman who does exactly that, they don’t withdraw the claim — they say, “well, no true Scotsman would.”
The same dodge plays out over something as small as a sports rivalry.
Jun: “Real fans of this team never boo the players.” Amir: “I’ve booed plenty of times, and I’ve followed them for fifteen years.” Jun: “Then you’re not a real fan.”
Jun’s original claim was about fans in general. Faced with a counterexample, he doesn’t revise it — he shrinks the definition of “fan” just enough to exclude Amir, so the claim survives untouched.
It shows up constantly in online arguments about expertise:
Comment: “No real programmer uses an IDE — real programmers use a plain text editor.” Reply: “I’ve shipped production code with an IDE for a decade.” Comment: “Then you’re not a real programmer, you’re just a coder who got lucky.”
Why the reasoning fails
The move looks like a clarification but it’s actually a rescue. A general claim gets falsified by a genuine counterexample, and instead of accepting that, the arguer quietly redraws the boundary of the group to exclude the counterexample — after the fact, with no independent justification for the new boundary. This makes the original claim unfalsifiable: any exception can just be defined away, so it can never actually be tested against reality. The purity word — “real,” “true,” “genuine” — isn’t doing descriptive work; it’s doing damage control.
How to respond
- Ask what the definition was before the counterexample: “Was booing already outside your definition of ‘fan,’ or did that just get added?”
- Name the shift: “That sounds like you’re redefining the group so the claim can’t be wrong.”
- Ask for a definition in advance: “What would it actually take for someone to count, before we hit another exception?”
- Recognize legitimate exclusions. A group can genuinely have defining criteria — a “vegetarian” who eats meat weekly isn’t really vegetarian. The fallacy is inventing the criterion on the spot to dodge one case, not having a criterion at all.