LSAT Fallacies: the Complete Flaw Encyclopedia

This encyclopedia covers the 18 logical flaws that show up on the LSAT. Each entry gives a plain-English definition, an original LSAT-style example, how to spot the flaw on test day, and what the right answer looks like next to the trap. Flaw questions are one of the most common LR types; strengthen and weaken questions test the same skill.

Flaw questions are one of the most common question types in Logical Reasoning. Strengthen, weaken, and assumption questions test the same skill from different angles. Every one of those moves starts with naming what went wrong in the argument.

This encyclopedia covers the 18 flaws that show up again and again. Each entry gives you a plain-English definition, an original LSAT-style example, how to spot it on test day, and what the right answer looks like next to the trap.

All examples are original. They are not real LSAT questions, and they do not come from our question bank.

All 18 fallacies

Ad Hominem Attacking the person instead of the argument. Straw Man Defeating a weaker version of the real argument. Equivocation One word used in two different senses. Correlation, Not Causation Two things happening together does not prove one causes the other. Part to Whole A fact about a part does not prove it of the whole. Begging the Question The conclusion is smuggled into the premises. Appeal to Authority An expert's word is not proof by itself. Appeal to Popularity Many believers do not make a claim true. Appeal to Tradition Old does not mean right. False Dilemma Two options are presented as if they were the only ones. Slippery Slope One step does not prove a chain of disasters. Hasty Generalization A tiny sample does not prove a big claim. Anecdotal Evidence One story is not proof. Red Herring An irrelevant topic dragged in to distract. Tu Quoque "You too" is not a rebuttal. No True Scotsman Redefining the claim to dodge a counterexample. Burden of Proof Not disproven is not the same as proven. Golden Mean The middle is not automatically right.

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Last updated October 12, 2026