No true Scotsman

No true Scotsman is when someone points out a counter-example to your general claim and you change the definition so the counter-example "doesn't count"—e.g. by saying only the "real" or "true" X would do that. Your claim becomes unfalsifiable but also empty: you're just defining the group so that anyone who doesn't fit is excluded. It's a way of refusing to learn from counter-examples.

Examples

• No Scotsman puts sugar on his porridge. — My uncle is Scottish and he does. — Then he's no true Scotsman.

• No real feminist would say that. — She calls herself a feminist. — Then she's not a true feminist.

• No good parent would allow that. — My neighbour allows it. — Then they're not a good parent.

• No real scientist would ignore the data. — Dr X did. — Then Dr X isn't a real scientist.

• No committed athlete would skip training. — He skipped yesterday. — Then he's not truly committed.