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April 1, 2022

Resist the Urge to Diagram on Logical Reasoning

Why Not Diagram?

One of the most commonly taught LSAT Logical Reasoning strategies is diagramming. You’ve probably seen it before—with arrows, squiggly lines, and abbreviations, Logical Reasoning diagrams look like a boatload of gibberish.

Consider this argument: “All elephants are pink. Dumbo is an elephant. Therefore, Dumbo is pink.” Another LSAT instructor may tell you to notate the argument as follows:

E → Pink and Not Pink → Not E

D → E and Not E → Not D 

Therefore, D → Pink and Not Pink → Not D

Maybe these notations make sense to you. Maybe they don’t. Either way, writing them down is counterproductive. It’s easier to understand an argument using common sense than to doodle it out. 

Given that “Dumbo is an elephant,” common sense tells us that if something is not an elephant, it can’t be Dumbo. Restating a conditional claim in this way is sometimes called identifying the “contrapositive,” but Thinking LSAT and LSAT Demon teachers avoid unnecessary jargon in lessons.

Diagramming takes a long time and is susceptible to mistakes. Time spent drawing arrows and rewording the exact same information in different ways could be better spent actually understanding the argument.

Understand the Argument in Your Own Words

If you get stuck on any part of an argument (in this case, if you can’t wrap your mind around the idea that all elephants are pink), try to visualize it. Don’t diagram it abstractly on paper, or you will only compound your confusion.