Study guide
This chapter covers two families of questions that ask you to read an argument with a critical eye rather than to change its strength. Flaw questions ask you to describe what has gone wrong with the author's reasoning, while inference and most-strongly-supported questions ask what can be properly concluded from a set of statements. Both question types reward precise, literal reading over general impressions, and both are frequently sabotaged by the same handful of predictable distractor patterns.
What a Flaw Question Actually Asks
A flaw question presents an argument and asks you to identify the specific error in its reasoning, usually phrased as which of the following describes a flaw in the argument's reasoning or the argument is vulnerable to criticism on the grounds that. Crucially, correct answers describe the reasoning error abstractly rather than restating the content of the stimulus; a correct answer might read the argument takes for granted that a correlation reflects a causal relationship, applying equally to an argument about ice cream sales and one about study habits. Your first job is the same as in Chapter 1: locate the conclusion and premises and name the gap between them. Your second job is to match that gap to a description, since the answer choices are abstract descriptions of reasoning patterns rather than paraphrases of the topic. A frequent trap is an answer choice that accurately describes something true about the passage's subject matter but does not describe an actual defect in the logic; such choices are almost always wrong on flaw questions, because the task is diagnosing faulty reasoning, not summarizing content. Practice translating concrete arguments into their abstract logical skeleton, for example turning most experts recommend X, so X must be correct into an appeal to authority that does not verify the experts' reasoning, since this translation skill is exactly what the answer choices demand.
Common Flaw Patterns
A small set of reasoning errors recurs across LSAT flaw questions, and recognizing them by name speeds up both the stimulus and the answer choices. Illicit conversion mistakes a conditional statement's direction or scope, for example treating all lawyers are licensed as if it also meant all licensed people are lawyers, or treating most as if it meant all. Unsupported causation occurs when an argument observes that two things are correlated, or that one event preceded another, and concludes without justification that one caused the other, ignoring the possibilities of coincidence, reverse causation, or a third factor causing both. Overreach, sometimes called an unwarranted leap, happens when a conclusion is broader, stronger, or more certain than the premises can support, such as moving from a claim about some members of a group to a claim about the whole group, or from a possibility to a certainty. Other recurring flaws include equivocation, where a key term subtly changes meaning between the premises and the conclusion; circular reasoning, where the conclusion is essentially restated as its own premise; and attacking the source of a claim rather than its content. Example: A study finds that towns with more fire trucks report more fire damage, and a columnist concludes that fire trucks cause fires. This is unsupported causation, since a more plausible explanation is that larger or more fire-prone towns both have more fire trucks and experience more fire damage.
Inference (Must-Be-True) Questions
Inference questions, often phrased as which of the following must be true on the basis of the statements above or if the statements above are true, which of the following must also be true, do not involve an argument at all in the traditional sense; the stimulus is simply a set of facts, and you must find the answer choice that is logically guaranteed by those facts. Because the correct answer must be true given only what is stated, the safest inference questions can be solved almost like a small logic puzzle, especially when the stimulus includes conditional statements. Watch particularly for chains of conditional statements, since combining them correctly (and only in the directions they actually license) often produces the correct inference, while combining them in the reverse direction produces an attractive wrong answer. The single most important discipline on inference questions is refusing to pick an answer that is merely plausible, common-sense, or consistent with the passage; the correct answer is the one that cannot be false if the stimulus is true. If you find yourself justifying a choice with well, that seems likely given what was said, you have likely drifted from must be true toward could be true, which is not what the question asked for.
Most-Strongly-Supported Questions
A close cousin of the inference question is the most-strongly-supported question, typically phrased as which of the following is most strongly supported by the statements above. This phrasing loosens the strict must be true standard slightly, permitting a correct answer that is very likely true given the stimulus rather than logically airtight, but it does not open the door to speculation. The correct answer is still the choice best anchored in the actual content of the stimulus, and every competing answer choice should be less well supported, not merely less interesting. A useful way to compare candidates is to ask, for each answer choice, how many additional unstated assumptions would be needed for it to be true; the most-strongly-supported answer typically needs the fewest additional assumptions layered on top of the stated facts. Distractors on these questions often extrapolate beyond the scope of the stimulus, for instance turning a factual claim about a specific city into a claim about cities in general, or converting a past-tense observation into a prediction about the future. Because the line between strongly supported and merely plausible can be subtle, always return to the exact wording of the stimulus and confirm the specific words used, rather than a loose paraphrase you have carried in memory from a first read.
Key terms
- Flaw question
- — A question type asking the test-taker to identify or describe the specific reasoning error in an argument.
- Illicit conversion
- — A flaw in which a conditional or quantified statement is reversed or its scope changed without justification, such as treating most as all.
- Unsupported causation
- — A flaw in which correlation or sequence between two events is treated as proof that one caused the other, ignoring alternative explanations.
- Overreach
- — A flaw in which the conclusion claims more, in scope or certainty, than the premises can support.
- Equivocation
- — A flaw in which a key term shifts meaning between its use in the premises and its use in the conclusion.
- Circular reasoning
- — A flaw in which the conclusion is assumed as, or restates, one of its own premises.
- Inference question
- — A question asking what must be true given only the facts stated in the stimulus, without evaluating an argument's persuasiveness.
- Must-be-true standard
- — The requirement that a correct inference answer cannot be false if the stimulus statements are true.
- Most-strongly-supported question
- — A question type asking for the answer choice best supported by the stimulus, allowing high likelihood rather than strict logical certainty.
- Conditional statement
- — A statement of the form if one condition holds, then a result follows, central to chaining inferences correctly.
Exam tips
- On flaw questions, translate the stimulus into an abstract description of the reasoning pattern before you read the answer choices, since correct answers rarely mention the stimulus's actual subject matter.
- Name the flaw type as you read; recognizing unsupported causation or illicit conversion by name is faster than re-deriving the error from scratch for each answer choice.
- On inference questions, reject any answer you can only justify with it seems likely; must be true is a stricter bar than seems plausible.
- When conditional statements appear in an inference stimulus, chain them only in the direction the logic actually licenses, and watch for answer choices built on the reversed chain.
- On most-strongly-supported questions, prefer the answer that requires the fewest additional assumptions beyond the stimulus's literal wording.