For a Must Be True question, choose the answer that follows from the information you are told to accept. A plausible answer is insufficient if the statements can all be true while that answer is false. The practical test is to locate the support or build a counterexample.
The stimulus may be a set of observations, conditional rules, or a passage that includes an argument. Do not assume every inference question is a formal-logic puzzle or that an argument can never appear. Read the stem to establish the task, then identify what the passage actually commits you to.
The labels below are teaching categories. The question's wording controls what you must establish.
| Task | Standard | Useful check |
|---|---|---|
| Must Be True | The answer must follow from the accepted information. | Can the statements all be true while this answer is false? If yes, reject it. |
| Most Strongly Supported | Choose the answer with the strongest support among the choices. | Compare the evidence for each answer; do not silently replace this task with a certainty requirement. |
| Could Be True | The answer must be compatible with the information. | Can you build at least one consistent situation where the answer holds? |
| Cannot Be True | The answer must conflict with the accepted information. | Do the statements rule it out? Merely lacking support is insufficient. |
Must Be True and Most Strongly Supported are related inference tasks, but they do not share the same proof requirement. A Cannot Be True question is a different task too; do not select a merely uncertain answer as if uncertainty established a contradiction.
This differs from a Necessary Assumption question, which asks what an argument depends on. Adding a helpful premise is also a different task from deriving an inference. If you are losing track of the author's claim, the main-conclusion guide addresses that separate skill.
The following examples were invented for instruction. They are not copied or adapted from an official LSAT question.
Statements: Every apartment in the Fairlawn building with a balcony has a south-facing window. No ground-floor apartment in that building has a south-facing window. Some ground-floor apartments were renovated last year.
What must follow? No ground-floor apartment in that building has a balcony.
The first rule says balcony → south-facing window. A ground-floor balcony would therefore require a south-facing window, which the second statement excludes. That contradiction rules out a ground-floor balcony. The renovation statement does not change the relationship.
| Proposed inference | Verdict | Reason |
|---|---|---|
| No ground-floor apartment has a balcony. | Must follow. | A balcony would require the window that ground-floor apartments cannot have. |
| Every south-facing apartment has a balcony. | Unsupported. | This reverses the first rule. A window does not establish a balcony. |
| Every upper-floor apartment has a south-facing window. | Unsupported. | The statements impose no such requirement on upper floors. |
| No renovated apartment has a balcony. | Unsupported. | Other renovated apartments could be upstairs and could have balconies. |
For the last claim, imagine a renovated upper-floor apartment with both a balcony and a south-facing window. Nothing in the statements forbids it. That counterexample defeats the proposed inference without proving that such an apartment actually exists.
Statements: Some museum volunteers speak French. Some museum volunteers work weekends.
Tempting answer: Some French-speaking museum volunteers work weekends.
It could be true, but it need not be. Suppose the museum has two volunteers: Lina speaks French and works only weekdays; Omar works weekends and does not speak French. Both statements hold, and the proposed overlap is absent.
Now add a different second statement: Every museum volunteer works weekends. With that stronger rule, the French-speaking volunteers must work weekends. The difference is the quantifier, not whether the imagined museum arrangement seems realistic.
| Mistake | What changes without permission | Correction |
|---|---|---|
| Reversal | “If A, then B” becomes “if B, then A.” | Keep the direction of the condition or use a valid contrapositive. |
| Invented overlap | Two “some” groups are assumed to contain the same members. | Try making the groups separate while preserving the premises. |
| Scope expansion | A claim about one population, period, or comparison becomes a broader claim. | Match each part of the answer to the corresponding evidence. |
| Real-world plausibility | A reasonable background belief becomes an unstated premise. | Ask what the passage itself licenses. |
| Rejecting a modest answer | A weakly worded but supported answer is dismissed for sounding uninteresting. | Judge whether it follows, not whether it sounds impressive. |
Our conditional-reasoning guide covers the first trap in more detail. Not every inference problem requires conditional notation; use it when the statements actually contain that relationship.
Before reading an explanation, write the exact statement or combination that would establish your answer. If you cannot find one, try a counterexample. After checking the correct reasoning, name the particular error: reversed rule, changed population, invented overlap, missed quantity, or something else specific.
Return to selected misses later and solve them without the explanation. Then use mixed practice so the category label does not do the task recognition for you. This is an instructional workflow, not a promise of a particular score gain or a claim that one review delay is scientifically optimal for the LSAT.
Use official questions for exam practice. LSAC's Logical Reasoning overview describes the broader skills assessed, and its preparation page links official practice. If you need another explanation system, compare the instructional approaches in our LSAT prep books guide.
LSAC's official preparation and Logical Reasoning pages were checked November 3, 2026. The teaching categories, original examples, counterexamples, and review procedure are Lovare editorial instruction. This guide does not forecast question-type frequency or convert learning-study effect sizes into LSAT score gains. This update removes the earlier unsupported dosage and timing inferences.
Written by Ali Unar, Lovare Institut. For individual review of recurring inference errors, see Lovare's LSAT coaching. Report corrections through our contact page.
September 20, 2026
September 20, 2026