Is the Fallacy Fallacy a Formal or Informal Fallacy?

Difficulty: What the heck

Is the fallacy fallacy a formal or informal fallacy?

Answer: it depends.

But first, briefly: the fallacy fallacy is the fallacy whereby the arguer concludes that an argument’s conclusion is false simply because the argument used to support it is fallacious.

For instance:

Debater 1: Trump is not evil, because you’re a cow.

Debater 2: Aha! That’s an ad hominem argument, and that’s fallacious. So you’re wrong that Trump isn’t evil. Therefore, Trump is evil.

Here, Debater 2 commits the fallacy fallacy by arguing that because Debater 1’s argument is a fallacious ad hominem abusive argument, Debater 1’s contention that Trump is not evil must therefore be false.

But the issue is this: just because someone’s reasoning is fallacious does not mean her conclusion is necessarily false. It does not mean it is true, either. It just means that the conclusion does not logically follow from that argument.

Think about it this way: if a kid were asked to do a multiplication problem—say, “2 × 2”—and, not knowing how to multiply, she used addition instead, she would still arrive at the right answer, “4,” even though her reasoning process would be wonky. It is the same way with logic and argumentation. A bad argument can accidentally land on a true conclusion.

However, the question I’ll have you ponder today is whether the fallacy fallacy is a formal or informal fallacy.

One way to interpret the fallacy fallacy is as relying on the following argument form:

Premise 1: If an argument is non-fallacious, then its conclusion is true.

Premise 2: This argument is fallacious.

Conclusion: Therefore, its conclusion is false.

If that is how the arguer is thinking, then sure: the fallacy fallacy can be understood as a formal fallacy. More specifically, it would have the form of denying the antecedent.

But here is another way to look at it. The arguer may instead be reasoning with a perfectly valid form—namely, modus ponens—while relying on a false premise:

Premise 1: If an argument is fallacious, then its conclusion is false.

Premise 2: This argument is fallacious.

Conclusion: Therefore, its conclusion is false.

If this is how Debater 2 is thinking, then the form itself is not the problem. The form is valid. The problem lies in Premise 1, which is false. In that case, the fallacy fallacy would be better understood as an informal fallacy.

So, is the fallacy fallacy a formal or informal fallacy?

Again: it depends on what, exactly, has gone wrong in the person’s reasoning.

And why does this distinction matter?

Because clarity matters. And because if we want to understand our own fallible thought processes, it helps to know whether the problem lies in the form of the reasoning or in the content of what we are assuming. But the psychology behind shitty logical reasoning is a topic for another day. Until next time, then.