search

Become an active member of our fallacy-discussing community (or just become a lurker!)

Commutation of Conditionals

(also known as: the fallacy of the consequent, converting a conditional)

Description: Switching the antecedent and the consequent in a logical argument.

Logical Form:

If P then Q.

Therefore, if Q then P.

Example #1:

If I have a PhD, then I am smart.

Therefore, if I am smart, then I have a PhD.

Explanation: There are many who could, rightly so, disagree with the first premise, but assuming that premise is true, does not guarantee that the conclusion is true.  There are many smart people without PhDs.

Example #2:

If I have herpes, then I have a strange rash.

Therefore, if I have a strange rash, then I have herpes.

Explanation: I am glad this is not true.  One can have non-herpes rashes.

Exception: If p=q, then it is necessarily true that q=p.

Tip: If you think might herpes, see your doctor.

References:

Pickard, W. A., & Aristotle. (2006). On Sophistical Refutations. ReadHowYouWant.com, Limited.

Questions about this fallacy? Ask our community!

Listen to the Dr. Bo Show!

Hello! I am social psychologist and author, Bo Bennett. In this podcast, I take a critical thinking-, reason-, and science-based approach to issues that matter. As of January 2020, this podcast is a collection of topics related to all of my books. Subscribe today and enjoy!

Visit Podcast Page