Fallacious: No True Scotsman

Here is a fun fallacy most people are familiar with: The No True Scotsman fallacy.

The No True Scotsman fallacy is actually not quite as simple as one might think and is actually a combination of several fallacies. Specifically, it relies on an arguer redefining a term in an ad hoc manner to make a desired assertion about it true.  Antony Flew in his book Thinking About Thinking used Scotsman as an example, hence the name:

Imagine Hamish McDonald, a Scotsman, sitting down with his Glasgow Morning Herald and seeing an article about how the “Brighton [(a town in England)] 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 [(a town in Scotland)] 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.”

Even though the No True Scotsman fallacy seems to be particularly about ad hoc redefining, often, people will not specifically redefine a term during the course of an argument but define a term in a way that they can use their definition to avoid being associated with a negative trait. It is also used to define a term in order to intentionally associate it with a positive trait. For example, a Christian might say, “Christians are all good people, and anyone who behaves badly is not a true Christian”. A conservative (such as Andrew Sclafly of Conservapedia) might say, “Conservatives, by definition, do not practice deceit.”  This commonly falls under the same umbrella as No True Scotsman, even though what the arguer is doing is initially defining “Christian” or “Conservative” in such a way as to exclude certain negative traits.

If an arguer is attempting to show that some people of a certain group behave badly, one cannot win an argument by simply defining said group as individuals who (among other things) do not behave badly. Similarly, if I want to argue that Christians are all jerks, I could define “Christian” to mean “someone who follows the Christian religion and is a jerk”. If someone were to make a counter-argument, pointing out that they are Christian but not a jerk, I could simply say that they are not a “true Christian”.

So, the No True Scotsman fallacy is employed when people are debating as to whether trait X is a necessary condition of belonging to group Y, and the person committing the No True Scotsman fallacy simply defines group Y as one in which membership requires trait X. Ones does not win such a debate in this way, as whether or not trait X is required for membership in group Y is the very matter under debate. So essentially, the No True Scotsman fallacy is a fallacy in which certain traits X are defined as essential to belonging to group Y before it has been established that this is the case.

Atheist example:

Arguer-A: No atheist would murder people.
Arguer-B: But atheist communists murdered 100 million people.
Arguer-A: Those people weren’t true atheists. True atheists would never murder 100 million people.

Theist example:

Arguer-A: Christians don’t support the abortion pill.
Arguer-B: But Andrea is a Christian and she supports Plan B.
Arguer-A: If that girl supports using the abortion pill, she isn’t a true Christian.

Arguer-A: Christians don’t believe in evolution.
Arguer-B: But the church I go to is Catholic and it says evolution is fact.
Arguer-A: Obviously Catholic’s aren’t true Christians.

Arguer-A: All atheists are immoral.
Arguer-B: But Ziztur is a very moral individual.
Arguer-A: Well then she obviously isn’t a true atheist.

Theist example that sounds like a No True Scotsman but isn’t:

Arguer-A: Christians believe Jesus existed.
Arguer-B: But Joe is a Christian and he says Jesus is a myth.
Arguer-A: If you don’t believe Jesus existed, then you’re not a true Christian.

Vegetarian example that sounds like No True Scotsman but isn’t:

Arguer-A: Vegetarian’s don’t eat meat.
Arguer-B: But Scott is a vegetarian and he eats fried chicken every Sunday at the VFW
Arguer-A: true vegetarian doesn’t eat fried chicken once a week.

Atheist example that sounds like No True Scotsman but isn’t:

Arguer-A: No atheist would murder people.
Arguer-A: Hitler was an atheist and he murdered lots of people.
Arguer-B: Hitler was not a true atheist. Hitler was Catholic. He talks about doing god’s work in his speeches and writings constantly.

This fallacy generally does not apply if there is a clear definition of a group, I.E. “An honest man would not lie to his wife about having an affair”.