Describe the
Flaw
Master the art of identifying and articulating reasoning errors in LSAT Logical Reasoning arguments.
What Is a Flaw Question?
A "Describe the Flaw" question asks you to identify the specific error in reasoning that an argument commits. The argument's premises may be perfectly true, but the conclusion still doesn't follow logically.
Flaw questions are among the most common question types on the LSAT, appearing 3 to 5 times per scored section. Mastering them is essential for a strong score.
Anatomy of a Flawed Argument
Why Flaw Questions Matter
The Core Flaw Categories
Top Flaw Types in Detail
Flaw vs. Weaken
| Describe the Flaw | Weaken | |
|---|---|---|
| What it asks | Name the reasoning error | Introduce new info that hurts |
| Answer type | Description of the error | A new fact or scenario |
| Correct answer is | Always already present in the stimulus | New information not in the stimulus |
| Key skill | Pattern recognition | Evaluating impact of new evidence |
| Common stems | "...flawed because it..." | "...most weakens..." |
How to Apply the Method
Example 1: Necessary vs. Sufficient
Stimulus: "All successful entrepreneurs are risk-takers. Jameson is a risk-taker. Therefore, Jameson is a successful entrepreneur."
Example 2: Correlation vs. Causation
Stimulus: "Studies show that people who eat breakfast every day tend to weigh less than those who skip it. Therefore, eating breakfast causes weight loss."
Example 3: Equivocation
Stimulus: "The governor said the new policy is 'fair.' But studies show the policy disproportionately affects low-income families. Something that disproportionately affects the vulnerable cannot be called 'just.' Therefore, the governor's claim is false."
Decoding Answer Choice Language
LSAT flaw answer choices use abstract, formulaic language. Learning to translate between your prediction and this language is critical.
More Answer Patterns
Common Mistakes
Flaw Type Reference Table
| Flaw Type | What It Does | Signal Phrase |
|---|---|---|
| Nec. / Suff. | Confuses a needed condition with a guarantee | "treats as sufficient" |
| Causal | Infers cause from correlation | "infers a causal relationship" |
| Equivocation | Shifts meaning of a key term | "in two different senses" |
| Ad Hominem | Attacks the person, not the claim | "based on characteristics of" |
| False Dichotomy | Presents only two options when more exist | "only possibilities" |
| Absence of Ev. | No evidence against = evidence for | "absence of evidence" |
| Circular | Conclusion restates the premise | "presupposes what it proves" |
Question 1 of 5
Argument: "Every great musician practiced for at least 10,000 hours. Marcus has practiced for 10,000 hours. So Marcus must be a great musician."
The reasoning in this argument is most vulnerable to criticism on the grounds that it:
Question 2 of 5
Argument: "Countries with more ice cream sales have higher rates of drowning. Therefore, ice cream consumption contributes to drowning deaths."
Which of the following best describes the flaw in this argument?
Question 3 of 5
Argument: "No one has proven that the new pesticide is harmful to human health. So it is safe for widespread agricultural use."
The reasoning in this argument is flawed because it:
Question 4 of 5
Argument: "Dr. Rivera argues that the city should invest in public transit. But Dr. Rivera doesn't even own a car and would personally benefit from better transit. Therefore, her argument for public transit investment should be dismissed."
The reasoning in this argument is most vulnerable to criticism because it:
Question 5 of 5
Argument: "The school board claims its new reading program is 'effective.' But a program that fails to improve standardized test scores cannot be called 'successful.' The data shows scores have not improved. Therefore, the school board's claim is wrong."
The argument's reasoning is flawed because it: