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No true Scotsman is a logical fallacy, meaning an error in reasoning, in which someone defends a generalization by redefining the criteria and dismissing examples that are contradictory.

It is also known as an “appeal to purity” as it aims to refute any arguments or evidence against a certain ideal by appealing to its “purity”. As such, this argument is used in an attempt to protect various groups from criticism, such as political parties and religious groups.

No True Scotsman - Example and definition


👉 No true Scotsman fallacy occurs when someone attempts to defend a universal claim by excluding any counter-examples for not being “pure” enough.

In other words, they reject instances that don’t fit into the category by changing the definition to a more specific one rather than acknowledging the evidence that contradicts the generalization.

Note that in this fallacy, “Scotsmen” can be replaced with any other group.

A typical logical form of a no true Scotsman- argument is:

  • All X are Y
  • (It is shown that not all X are Y)
  • All true X are Y

👉 The example this fallacy is named for goes as follows:

Angus: “No Scotsman puts sugar on his porridge.”
Scotty: “But my uncle is a Scotsman and he puts sugar on his porridge.”
Angus: “But no true Scotsman puts sugar on his porridge!”

Here, Angus changes the definition of his generalization attempt in ad hoc fashion and simply dismisses Scotty’s counter-example.

Use of No True Scotsman

This type of argument is common and can be made for any group. For instance, it is often used to defend a particular religious group by excluding those who behave in unfavorable ways as not “true” members of the religion.

This can also be seen as an example of cherry-picking, although in reverse; rather than choosing only the examples that are beneficial, one denies all the disadvantageous ones.

Antony Flew, who first mentioned the no true Scotsman fallacy and coined the term, gave the following explanation in his book Thinking About Thinking: Or, Do I Sincerely Want to Be Right?:

Imagine Hamish McDonald, a Scotsman, sitting down with his Glasgow Morning Herald and seeing an article about how the ‘Brighton Sex Maniac Strikes Again’.

Hamish is shocked and declares that ‘No Scotsman would do such a thing’. The next day he sits down to read his Glasgow Morning Herald again; and, this time, finds an article about an Aberdeen man whose brutal actions make the Brighton sex maniac seem almost gentlemanly.

This fact shows that Hamish was wrong in his opinion, but is he going to admit this? Not likely. This time he says: ‘No true Scotsman would do such a thing’.

Not Fallacious

This fallacy does not occur if there is a clear and accepted definition of the group and what it requires to belong to that group, and this definition is violated by the arguer. For example:

  1. “No vegetarian eats meat.”
  2. “Well, my friend says she is a vegetarian but she still eats meat.”
  3. “But no true vegetarian eats meat.”

This is not a fallacy because being a vegetarian, by definition, is the practice of abstaining from the consumption of meat; if she consumes meat, she is not really a vegetarian. Thus, this fallacy can only occur in a situation where the definition can be redefined due to a lack of clear understanding or agreement of the criteria.