Flaw in the Reasoning Questions
The argument is broken. Your job is to say exactly where.
Two tools pair with this method. The miss-pattern analyzer shows which question types cost you the most points, and the blind review worksheet gives you a second pass at every miss.
What the question asks
The question asks you to find what is wrong with the argument. The stem says something like "The reasoning is most vulnerable to criticism because..." or "The argument commits which one of the following flaws?"
You are not asked whether the conclusion is true. A conclusion can be true for bad reasons. You are asked what is wrong with the reasoning that leads to it.
Step-by-step method
- Find the conclusion. Ask what claim the author is trying to sell you. Ignore the evidence for a moment and pin down the point.
- Find the evidence. Ask what facts the author offers in support. Keep it short. Most LSAT arguments give one or two premises.
- Name the gap. Ask what the author assumes without saying. The gap between evidence and conclusion is where the flaw lives.
- Predict the flaw in plain words. Before you read the choices, say the flaw to yourself in everyday language. "It attacks the person, not the plan." Prediction beats recognition.
- Match your prediction. Find the choice that says the same thing in formal language. Avoid choices that restate evidence or describe a flaw the argument never commits.
Worked examples
Both examples are original. They are not real LSAT questions.
Example 1
The city council should reject the new park proposal. Councilor Dana, who proposed it, was cited for tax fraud last year.
The reasoning is flawed because it...
The answer: attacks the proposer instead of the proposal.
Why: Dana’s tax history says nothing about whether the park is a good idea. The argument targets the person, not the plan. That is an ad hominem attack: rejecting a claim because of who made it.
Example 2
People who eat breakfast every day report lower stress. So eating breakfast must reduce stress.
The argument is most vulnerable to criticism on the grounds that it...
The answer: confuses correlation with causation.
Why: Breakfast eaters may differ in other ways. They may sleep more or have calmer mornings. The argument assumes the link runs in one direction without ruling out other explanations for the pattern.
Reading flaw answer choices like an editor
Flaw answer choices are written in formal language on purpose. Phrases like "presumes, without justification," "takes for granted," and "fails to consider" all do the same job: they point at the gap between the evidence and the conclusion. Learn this vocabulary cold. On test day you will not have time to decode it from scratch.
Most flaw choices fall into three buckets. First, choices that describe a real flaw this argument does not commit. These are the most tempting. They sound like criticism, and they use the right vocabulary, but they point at a gap that is not there. Second, choices that restate a premise as though the premise itself were the problem. A true premise is never a flaw. Third, choices that attack a claim the author never made. Before you pick a choice, ask: does this describe what this argument actually did? If you cannot point to the spot in the argument, do not pick it.
The fastest way to get better at flaw questions is to write your own prediction first. After you name the gap, say the flaw in plain words: "It assumes the survey represents everyone." Then match that plain sentence to the formal choice. "Generalizes from an unrepresentative sample" is the same sentence in a suit. Students who skip the prediction step end up choosing between two choices that both sound plausible. Students who predict usually find one choice that matches and four that do not.
Common traps
- A choice that restates a premise as if it were the flaw. True premises are not flaws.
- A choice describing a real flaw the argument does not commit. Read what the argument actually does.
- A choice attacking a claim the author never made. Straw men are for other questions.
- "Fails to consider" choices where the missing fact would not change anything.
Practice the method
The free diagnostic scores every LR question type and shows exactly where you are losing points.