You Want Me to Believe What?!

2 minute read

Close up of The Thinker

Post hoc ergo propter hoc. Ad hominem. Ad populum. Is this a Latin class or a GMAT blog? What if I said straw man or red herring or slippery slope? That last one might ring a bell, but the rest probably leave you scratching your head. These are all examples of logical fallacies that undermine an argument, and yet are constantly used by people as supposedly valid reasoning. Here are some examples you may have heard recently from people you interact with.


Begging the Claim (using the claim as the conclusion)

                       That inefficient and incompetent project manager should be fired.

Circular Argument (restating rather than proving)

                       Companies should hire efficiency consultants because they make offices more functional.

Red Herring (diverting from the real issue)

                       We may be a few days behind schedule on this project, but what about the salesmen missing their quotas the last two quarters?

Straw Man (oversimplifying a viewpoint)

                       The CEO of the internet company banned working from home because she dislikes working moms.

Hasty Generalization (a conclusion based on insufficient evidence)

                       The company’s stock dropped ten percentage points yesterday, so the investors are all going to end up bankrupt.

Moral Equivalence (comparing a minor offense to a major one)

                       My boss is so cheap with distribution of office supplies that she’s like a female Stalin.


One of the goals of critical reasoning questions on the GMAT is to measure your ability to identify reasoning errors that are committed in making an argument. Of course, in reality no one is going to ask you to select the valid response from a list of five possibilities, but someone will make a logically unsound statement in defense of a point and hope that you just accept it. For example, that p_ost hoc ergo propter hoc_ I mentioned before…let’s take a look:

                       The company instituted a new, casual office dress code and then employee productivity rose so the dress code must have been the reason for increased productivity.

If you’ve been practicing your critical reasoning questions this type of argument should look very familiar. That’s right – it’s a causal argument. One event occurred and another followed, so the first must have caused the second. This is a very convenient type of reasoning in which someone ignores all the other possible factors because they he wants to promote a certain policy or action, in this case a casual dress code.

While the range of logical fallacies in reality goes beyond the scope of what is tested on the GMAT, familiarity with some will help you identify others. And by eliminating such fallacies from your arguments, you will become a more convincing and credible speaker.

Want to try your hand at identifying some logical fallacies? Try this exercise from Penn State or this one from Carson-Newman University.


 Image Courtesy of Brian Hillegas with Creative Commons License.