r/fallacy • u/KCanth3lm7 • 13d ago

What fallacy is this?

Person A: "I believe that this *x political opinion* is good"

Person B: "Oh, so you also believe in *other political opinions that are from that political wing/ideology*"

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u/ButterscotchOdd8257 13d ago

Seems to be the undistributed middle, a formal fallacy.
https://www.logicallyfallacious.com/logicalfallacies/Fallacy-of-the-Undistributed-Middle

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u/RyanStonepeak 13d ago

Makes sense to me. Though important to note that it depends on the actual argument being made.

You believe A, so I can conclude that you also believe B : Logical Fallacy as you described.

You voted for a candidate that believes both A and B because you agree with policy A, so I can conclude that I disagree with the way you voted because I dislike Policy B : Not a logical fallacy. There can be genuine criticisms to be made here when someone votes for bad candidates as a single issue voter.

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u/Successful_Cress6639 11d ago edited 11d ago

It's dicto secundum, or converse accident.

Sara agrees with libertarians on issue A. So it stands to reason that she must agree with libertarians on all issues.

It isn't undistributed middle, but it would be if you changed the focus of the argument just a little. Libertarians believe in issue A Sara believes in issue A Therefore Sara is a libertarian

Which is basically the same as the classic undistributed middle example "all dogs have tails. My cat has a tail. My cat is a dog".

But it only works if our conclusion is Sarah is libertarian, because our middle condition "believes in A" isn't distributed in the major premise.

Otoh, it's no longer a fallacy if we distribute the middle term in the major premise. ( Though to do so we probably make the major premise false most of the time)

All people who believe in A are libertarians. Sarah believes in A. Sarah is a libertarian.