I like 100%ing things, so I decided to do every single LSAT flaw question this week and categorize them all. Enjoy:
Part I: The "Big Hitters" (>6 Occurrences)
These are the flaws that appear most often on the LSAT. Mastering these is non-negotiable for a high score. They are listed below in order of frequency.
| Flaw Name | Count | The Concept | Example | The Gap |
|---|---|---|---|---|
| Exclusivity (False Dilemma) | 70 | Assuming only two options exist when there might be a third. | "To keep the library open, we need more tax revenue. But citizens will revolt if we raise taxes. Therefore, we must close the library." | What about option C? Increase the tax base through new business. |
| Unique/Rare Assumption | 44 | Making a specific assumption that bridges two uncommon concepts. | "We have enough steel to build the bridge. Therefore, we can improve tourism." | No actual connection between bridge construction and tourism. |
| Hasty Generalization | 43 | Drawing a broad conclusion from a small, biased sample. | "My grandfather smoked and lived to 104. Therefore, smoking isn't bad." | Sample size of one outlier. Survivorship bias. |
| Correlation for Causation | 38 | Assumes that because A and B happen together, A causes B. | "People with expensive espresso machines have less heart disease. Therefore, espresso protects against heart disease." | Common cause: wealth. Wealthy people afford both. |
| Ad Hominem | 31 | Attacking the person rather than the argument. | "The Mayor says crime dropped, but he's running for reelection." | Motive doesn't change the statistical facts. |
| Necessary vs. Sufficient | 28 | Treating a requirement as a guarantee. | "To win the lottery, you must buy a ticket. I bought a ticket. Therefore, I'll win." | Having the requirement doesn't guarantee the result. |
| Numbers vs. Rates | 22 | Assuming a larger raw number means a larger rate. | "More people die in hospitals than in pistol duels. Therefore, duels are safer." | The rate of death matters, not the raw number. |
| Flawed Analogy | 21 | Comparing two things not alike in the way that matters. | "Running a government is like running a family. Parents don't let kids vote on bedtime. Therefore, the President shouldn't let citizens vote." | A family and a democracy are fundamentally different. |
| Mistaken Reversal | 19 | Given A → B, concluding B → A. | "Rain makes sidewalks wet. The sidewalk is wet. Therefore, it's raining." | Could be sprinklers or a spilled bucket. |
| Mistaken Negation | 18 | Given A → B, concluding ~A → ~B. | "A 180 gets you into law school. John didn't get 180. Therefore, John won't get in." | A 180 is sufficient, not the only way in. |
| Argument from Ignorance | 17 | Because a claim hasn't been proven true, it must be false (or vice versa). | "Scientists can't prove ghosts don't exist. Therefore, ghosts are real." | Absence of evidence is not evidence of absence. |
| Equivocation | 17 | Using a key word in two different definitions. | "The story generated 'public interest' (curiosity). Therefore, it's in the 'public interest' (societal benefit) to release suspect names." | The word shifted meaning mid-argument. |
| Part-to-Whole | 17 | Because parts have a property, the whole must have it. | "Every player is a superstar MVP. Therefore, the team will be the best in the league." | Ignores team chemistry and coaching. |
| One-Sided Net Effect | 14 | Looking only at pros (or cons) and ignoring the net outcome. | "This medicine causes nausea. We shouldn't use it to cure this deadly disease." | Ignores the massive benefit (curing death). |
| Whole-to-Part | 12 | Because a group has a property, every member must. | "The building is circular. Therefore, every apartment must be circular." | Units could be wedge-shaped or rectangular. |
| Knowledge vs. Reality | 12 | Confusing what is believed with what is true. | "People in the Middle Ages believed the earth was flat. Therefore, it was flat." | Belief does not shape reality. |
| Quantifier Shift | 11 | Shifting from "every X has a Y" to "there is one Y for all X." | "Every person has a mother. Therefore, there is one woman who is the mother of every person." | Individual relationships don't collapse into a single universal. |
| Reversed Causality | 10 | Gets the causal direction wrong. | "Successful people drive expensive cars. Therefore, buy an expensive car to become successful." | Success buys the car, not the reverse. |
| Incomplete Cause | 9 | Attributing a result to one cause when multiple factors are needed. | "The fire was caused by the match. Therefore, oxygen was irrelevant." | Ignores other necessary factors. |
| Rejecting Conclusion (Bad Argument) | 9 | Because the argument for a conclusion is bad, the conclusion must be false. | "My opponent says lower taxes because unicorns. Since unicorns aren't real, we shouldn't lower taxes." | A bad argument doesn't disprove the conclusion. |
| Straw Man | 9 | Distorting an opponent's argument to make it easier to attack. | "My opponent proposes a 2% military cut. Apparently they want us defenseless!" | Twisted "small cut" into "defenseless." |
| Temporal Flaw | 9 | What was true in the past will be true in the future. | "Profits increased every quarter for 5 years. Therefore, they'll increase next quarter." | Ignores changing circumstances. |
| Misinterpreting Evidence | 8 | Misreading data to support an unsupported conclusion. | "The text says 'some' like pizza. Therefore, 'most' like pizza." | Exaggerated the strength of evidence. |
| Exaggerating Conclusion | 7 | The conclusion is stronger than the evidence allows. | "It's possible it will rain. Therefore, it will definitely rain." | Possibility treated as certainty. |
Part II: The Minor Flaws (≤ 6 Occurrences)
- Circular Reasoning (6): The conclusion restates the premises.
- Failure to Address the Claim (6): Ignores the opponent's actual point.
- Flaw of Degree (6): Treating a continuum as binary.
- Confusing Intent with Effect (5): Assumes actual outcome was the intended outcome.
- Flawed Experiment (5): Biased experimental design.
- Misapplication of a Principle (5): Incorrectly applies a general rule.
- Appeal to Inappropriate Authority (4): Cites an irrelevant expert.
- Confusing Relative and Absolute Values (4): Treats ranking changes as quality changes.
- Ignoring the Counterfactual (4): Doesn't consider what would have happened without the cause.
- Internal Contradiction (4): The argument's premises are internally inconsistent.
- Math Flaw / Unstated Assumption (4): Assumes proportional relationships without justification.
- Unrepresentative Methodology (4): Polls the wrong population.
- Error of Aggregation (3): Aggregated data masks subgroup differences.
- Ignoring a Common Cause (3): Two correlated events both caused by a third.
- Appeal to Popular Opinion (2): True because many believe it.
- Confusing Average with Distribution (2): Outliers skew an average.
- Genetic Fallacy (2): Judging by origins rather than current properties.
- Hasty Generalization — Overextrapolation (2): Assumes a trend continues indefinitely.
- Perfect Solution Fallacy (2): Rejects a partial solution because it's not complete.
- Plurality vs. Majority Flaw (2): Plurality treated as majority.
- Slippery Slope (2): One modest action will trigger a disastrous chain reaction.
- Appeal to Consequences (1), Appeal to Emotion (1), Appeal to Tradition (1), Biased Evidence (1), Confusing Beneficiaries with Cause (1), Confusing Consistency with Accuracy (1), Confusing Discovery with Occurrence (1), Inferring Necessity from Correlation (1), Overlooking Contributing Factors (1), Resolving Contradiction Arbitrarily (1)
And that's them all that I know of. Found any others among the evaluate, strengthen, weaken, or assumption questions? Drop them in the comments!