which one of these is a fallacy of irrelevance?

Question

a. We all took geography, so one of us should remember the difference between longitude and latitude.
b. He doesn’t want to watch the game, so he must not be that interested in sports.
c. You’re a math professor, so you must do your own taxes.
d. All these answers are correct.

Answer 1

The fallacay of irrelevance is an informal fallacy, so it is not as well defined as certain formal fallacies. So take my answer with a grain of salt, for it almost certainly depends on what sources your teacher is using.

 

But I would pick C. In choice A it just seems that the conclusion does not follow from the premise necessarily, not that the premise is irrelevant. For Choice B, whether someone is interested in watching sports does feel like it is relevant to whether someone would watch sports. This feels like the fallacy where you incorrectly apply a specific situation to create a general rule (can't remember its exact name, but it is indeed a specific fallacy). I feel so confident that choice B is not correct that I do not think D can be correct. In choice C, though, there is no specific connection between doing your own taxes and what your job is. Someone of any profession could do their taxes and someone from any profession might not do their own taxes. It does not seem like relevant information.

 

But again, the fallacy of irrelevance is a really broad category that can encompass many more specific fallacies, such as the appeal to authority or the appeal to consequences. So I do not think someone who does not know what your professor means specifically by that phrase can give you an answer with any confidence. It is possible his/her definition is broad enough that it somehow includes all three, for a really stubborn philosophy major could argue that MOST informal fallacies are fallacies of irrelevance.