Defining the No True Scotsman Fallacy

If Google searches are any indication, the term "No True Scotsman Fallacy" (from informal logic) is fairly widely known. At the same time, there seems to be considerable disagreement about how to define it. This is odd, because the No True Scotsman Fallacy takes its name from a specific example given by Antony Flew:

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."

The various definitions that have been advanced cannot all simultaneously apply to Flew's example. In this blog post, I try to find a definition of the NTSF that actually captures what's going on in that example.

1. Definition 1: ad hoc rescue

The Internet Encyclopedia of Philosophy defines the NTSF as "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". Glancing at the Internet Encyclopedia of Philosophy's definition of "ad hoc rescue", I found the following:

When faced with conflicting data, you are likely to mention how the conflict will disappear if some new assumption is taken into account. However, if there is no good reason to accept this saving assumption other than that it works to save your cherished belief, your rescue is an ad hoc rescue.

Example:

Yolanda: If you take four of these tablets of vitamin C every day, you will never get a cold.

Juanita: I tried that last year for several months, and still got a cold.

Yolanda: Did you take the tablets every day?

Juanita: Yes.

Yolanda: Well, I’ll bet you bought some bad tablets.

Notice that the encyclopedia defines an ad hoc rescue as a maneuver designed to preserve one's original claim: Yolanda doesn't want to give up her original claim that vitamin C tablets prevent colds, so she makes the ad hoc assumption that Juanita bought bad (i.e. expired or fake) vitamin C tablets. Thus, the Internet Encyclopedia of Philosophy apparently regards the NTSF as a maneuver designed to preserve one's original claim.

In Flew's example, was Hamish McDonald trying to preserving his original claim? I don't think so. Granted, Flew himself says that Hamish was refusing to "admit" that he was "wrong in his opinion": this seems to imply that Hamish was trying to preserve his original claim. But I think Flew may be failing to draw an important distinction here. What exactly was Hamish's original claim? When Hamish first said, "No Scotsman would do such a thing", he was presumably using the word "Scotsman" to refer to any legal citizen of Scotland. In that case, Hamish's original claim was that no legal citizen of Scotland would do such a thing. Now, notice: when Hamish sees the newspaper story about the Aberdeen man, he doesn't challenge the newspaper's factual accuracy; he doesn't deny that the Aberdeen man is a citizen of Aberdeen, Scotland. Thus, Hamish clearly isn't trying (consciously, at least) to preserve his original claim. Rather, Hamish is changing his claim by changing his use of the term "Scotsman". After learning about the Aberdeen man, Hamish says, "No true Scotsman would do such a thing", where a "true Scotsman" is not just any legal citizen of Scotland but, rather, someone who truly embodies what Hamish regards as Scottish values.

I conclude that the Internet Encyclopedia of Philosophy's definition of the NTSF fails to capture what's going on in Flew's example.

2. Definition 2: ad hoc change

Sometimes the NTSF is defined as the act of responding to counterexamples by making an ad hoc change to one's claim.[1] Understood broadly enough, this definition does apply to Flew's example. After all, Hamish does change his claim, and he does change it specifically in response to the counterexample provided by the Glasgow Morning Herald.

However, there are two problems here. First of all, if we define the NTSF as encompassing any ad hoc change designed to accommodate counterexamples, then it isn't clear to me that every case of the NTSF is really a fallacy. (I suppose it depends on what we mean by "ad hoc"—an issue that I don't wish to get tangled up in at the moment.)

Second, if we define the NTSF as the act of making an ad hoc change to one's claim, then the connection between the NTSF and Flew's example becomes tenuous at best. Consider the following scenario:

The Swan Scenario

John: "No swan is black."

Tim: "But I saw a black swan in my backyard yesterday."

John: "Okay, then; no swan except the one in your backyard is black."

The Swan Scenario clearly fits our current definition of the NTSF, since John makes an ad hoc change to his claim in order to accommodate Tim's counterexample. But there is otherwise no parallel between the Swan Scenario and Flew's example. In Flew's example, Hamish says, "No true Scotsman would do such a thing". But in the Swan Scenario, John doesn't say, "No true swan is black"; rather, he says, "No swan except the one in your backyard is black". Again, the parallel with Flew's example is tenuous at best.

3. Definition 3: ad hoc redefinition

In Medical Ethics: A Very Short Introduction (Oxford UP, 2004), Tony Hope defines the NTSF as follows:

What seems to be a statement of fact (an empirical claim) is made impervious to counter-examples by adapting the meaning of words so that the statement becomes true by definition and empty of any empirical content.

Antony Flew himself gives essentially the same definition in A Dictionary of Philosophy (NY: St. Martin's Press, 1984), p. 251:

A maneouver that meets the falsification of some cherished generalization by maintaining that the predicate in question, while not perhaps applicable to all run of the mill so-and-sos, is nevertheless essential to true so-and-sos. […] This [is a] piece of arbitrary redefinition.

This definition finally captures what's going on in Flew's example. In Flew's example, Hamish first says, "No true Scotsman would do such a thing"; then, when confronted with a counterexample, he says, "No true Scotsman would do such a thing", where a "true Scotsman" is apparently someone who truly embodies Scottish values (or something like that): here Hamish is clearly redefining the term "Scotsman" (or "true Scotsman") in such a way that it's true by definition that no Scotsman would do such a thing.

We can summarize this definition of the NTSF as follows: the NTSF is a maneuver in which one responds to a counterexample to the claim "All A are B" by (tacitly) redefining "A" so that the claim becomes true by definition.

4. A fallacy?

Thus defined, the NTSF doesn't seem to be a fallacy, strictly speaking.[2] That is, the NTSF doesn't involve any kind of faulty reasoning. Indeed, one who engages in an ad hoc redefinition can't possibly be accused of faulty reasoning, since redefining a term is not itself a case of inference. If there's a problem with the NTSF, it doesn't consist in any kind of argumentative fallacy.

As Flew (1984, 251) himself notes, the real problem with the NTSF "is that the manoeverer may persuade himself, and others, that this piece of arbitrary redefinition has shown the original contingent contention after all not to be false". Or, in simpler English, if Hamish tells himself that no "true" Scotsman (i.e. no one who truly embodies Scottish values) would do X, then he may remain dangerously oblivious to the fact that there are many "false" Scotsmen (i.e. many people who have Scottish citizenship but who would not hesitate to violate "Scottish values").

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[1] One David Matheson appears to use this definition in his An Introduction to the Study of Education (London: Routledge, 2008). There Matheson defines the NTSF as the fallacy of making an "ad hoc change to shore up [one's] assertion" (2008, 350).

[2] Interestingly, neither Hope in his Medical Ethics nor Flew in his Dictionary actually use the expression "No True Scotsman Fallacy": both instead refer to the "no-true-Scotsman move" (although Hope does refer to this move as a "fallacy").