No true Scotsman
Also called: Redefining the group
Protecting a claim by redefining the group so counterexamples don't count.
How to spot it
Did the definition change right after someone gave a counterexample?
Example
“No honest person would cheat on taxes.” “My neighbour did.” “Then he wasn't really honest.”
How to answer it
Ask for the definition before looking at examples.
Related
- Moving the goalposts: Changing what would count as proof after the earlier standard has been met.
- Begging the question: Using the conclusion as one of the reasons for the conclusion.