Talk:No True Scotsman

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I don't think I agree with this, from the "Exceptions to the rule" section:

"When the amendment to the definition is actually a necessary condition for membership in the class, this type of argument is not a fallacy."

In the example then given, "not eating meat" is the implicit "ammendment to the definition," (of vegetarian), when that is NOT an ammendment, but part of the actual dfinition of vegetarian.

Perhaps it is just the example I disagree with, but I think I actually disagree with the whole "exception" as discussed.\

Thoughts?

I think you may be overanalyzing the word "amendment" in this context; you are of course correct that "not eating meat" does not, strictly speaking, change the definition of "vegetarian." It is, however, a restatement of the definition in different words than were previously used.

In context, however, the point is that the fallacious and non-fallacious arguments are superficially similar, as follows:

• No X would Y
• A does Y
• Therefore, A is not an X

The question is whether, in this context, the statement "No X would Y" is in fact tautological. If so, the argument is valid; if not, the argument is a fallacy (even if the statement "No X would Y" is observationally true). But the only way for the statement to be tautological is for not-Y to be a necessary component of X. It is important to distinguish these superficially similar cases. -- Dr Kitten

I changed the exception slightly, to address rslancastr's objections. I think had actually originally intended "not eating hamburgers", which is more than a restatement of "being vegetarian".