No true Scotsman is a logical fallacy and more specifically a special case of circular logic. It involves making an assertion and dismissing any counterexamples because they contradict the assertion. Thus, the person making the assertion can refuse to admit that the assertion is falsifiable.
The Internet Encyclopedia of Philosophy describes the no true Scotsman fallacy thus:
|“|| No True Scotsman
This error is a kind of ad hoc rescue of one's generalization in which the reasoner re-characterizes the situation solely in order to escape refutation of the generalization.
Smith: All Scotsmen are loyal and brave.
Jones: But McDougal over there is a Scotsman, and he was arrested by his commanding officer for running from the enemy.
Smith: Well, if that's right, it just shows that McDougal wasn't a TRUE Scotsman.
The standard example, and the one that gives the fallacy its name, is as follows:
- "No Scotsman puts sugar in his porridge."
- "Sean is a Scotsman and puts sugar in his porridge."
- "Then Sean is not a true Scotsman, as no true Scotsman puts sugar in his porridge."
More generally, the fallacy works like this:
- "Every A is a B."
- "Here is an example of an A that is not a B."
- "Your example cannot actually be an A, since every A is a B."
The argument thus collapses into a tautology.
The following are real-world examples:
- "The Soviet Union was not a truly Communist country, as truly Communist countries would not have been so brutal and repressive."
- "The 9/11 terrorists were not true Muslims, as Islam is a religion of peace."
People employing the fallacy are not necessarily consistent. For example, they may argue that the Soviet Union was a truly Communist country when they find something to like about it, but not when its atrocities and failings are pointed out to them.
The fallacy is not committed when the term has a clear and accepted definition and the example falls outside of that definition. For example, someone saying that no true monotheist believes in multiple gods does not commit the fallacy, since the clear and accepted definition of a monotheist is someone who believes in only one God.
Every true Scotsman
While the classic version of the no-true-Scotsman fallacy redefines categories to exclude inconvenient examples, the fallacy also includes redefining categories to include desirable "examples" that are not actually examples. For instance, Bernie Sanders insists that Denmark is a socialist country, even as that country's prime minister says otherwise.