Must-Be-True Questions
Key Takeaways
- Must-Be-True answers are forced by the stimulus; plausible outside explanations are not enough.
- The safest credited answers are often modest restatements, combinations, or contrapositives rather than broad conclusions.
- Quantifiers, conditional direction, and exact scope control what can and cannot be inferred.
- On current LR sections, strict inference discipline prevents true-but-unsupported answer choices from stealing time.
The Forced-Inference Standard
A Must-Be-True question is one of the cleanest accepting-mode tasks in Logical Reasoning. LSAC describes LR as a section built around short ordinary-language arguments and facts. On this task, you are not asked to repair, attack, or judge the passage. You are asked what the passage already commits you to.
The credited answer must be supported by the stimulus with no extra assumption. It may be a direct restatement, a combination of two facts, a valid conditional inference, or a limited consequence of a quantity statement. If the answer merely sounds likely, useful, or consistent, it is not enough.
Stem Signals
| Stem language | Practical meaning | Main danger |
|---|---|---|
| must be true | forced by the text | choosing what is merely plausible |
| properly inferred | follows from stated facts | adding outside knowledge |
| logically follows | valid result of premises | reversing a rule |
| can be concluded | supported conclusion only | overclaiming scope |
Read the stimulus in accepting mode. Treat every statement as given, even if you disagree with it. LSAC's own guidance says to answer on the basis of the information provided and not to pick a response just because it is true. That warning is especially important here.
Modest Answers Win Often
The correct answer on a hard Must-Be-True item often feels less dramatic than the wrong answers. If the stimulus says all certified interpreters passed a screening and Maya is a certified interpreter, you can infer Maya passed the screening. You cannot infer Maya is highly skilled, the screening is fair, or all people who passed are certified interpreters.
That modesty is not a weakness. It is the standard. The test rewards restraint because the wrong answers often use the same topic with stronger force.
Common Inference Moves
| Stimulus gives | You may infer | You may not infer |
|---|---|---|
| all A are B; X is A | X is B | all B are A |
| no A are B; X is A | X is not B | X is the only non-B |
| most A are B; most A are C | some B are C | most B are C |
| P only if Q; not Q | not P | Q proves P |
| some A are B | at least one A is B | most A are B |
When quantity appears, slow down. Some means at least one. Most means more than half. All means every member. Many and usually are less precise and rarely support exact numerical claims.
Combine, Do Not Embellish
Many Must-Be-True questions require combining two or three statements. Suppose a rule says every clinic that receives a city grant must publish patient-language notices, and another fact says the Eastside clinic received such a grant. The required inference is that Eastside must publish those notices. No claim about quality of care, patient satisfaction, or the wisdom of grants follows.
The best mental process is small and mechanical:
- List the rule or fact with exact force.
- List the item or group the rule applies to.
- Apply only the licensed direction.
- Reject answers that add cause, motive, value, or frequency not stated.
If the stimulus contains an argument, do not evaluate the gap unless the stem asks for it. A Must-Be-True answer can be based on a premise, an intermediate conclusion, or even a flawed author's statement. Your task is not to make the argument sound.
Wrong Answer Patterns
The most tempting wrong answers are compatible with the passage. Compatibility is too weak. If the passage says a neighborhood garden opened before complaints fell, it is compatible that the garden caused the decline. But unless the passage rules out other causes or states the causal link, causation does not have to be true.
Another trap is a real-world generalization. A statement about a city budget may make it tempting to infer politics, taxes, or voter reaction. Unless the stimulus supplies those facts, they are outside the text.
Scope shifts matter. A fact about applicants who completed training does not cover all applicants. A rule about nonprofit theaters does not cover every cultural organization. A claim about average processing time does not prove every individual case improved.
Exam-Speed Method
On test day, read for proof, not persuasion. Underline or mentally mark all, no, some, most, only if, unless, except, before, after, and comparative terms. Those words usually determine the answer.
For conditional language, take the contrapositive only when valid. If admission requires a fee, then admission implies fee paid. No fee means no admission. Fee paid alone does not mean admission.
For fact sets, ask what must be common to the groups mentioned. For arguments, ask which statement follows from the stated claims regardless of whether the author's reasoning is strong.
One useful review habit is to mark why an answer is not forced. Label it as possible, too broad, reversed, or outside. Those labels build the precision that lets you solve later inference items without rereading every choice.
The current LSAT has two scored LR sections, so strict inference habits repeat across many scored questions. Must-Be-True accuracy is built from disciplined restraint: accept the text, combine only what it gives, preserve force, and avoid the attractive answer that would need one more premise.
A grant rule says that every project funded by the Heritage Fund must have a community partner and must publish a public report. Some oral-history projects were funded by the Heritage Fund. No privately archived project publishes a public report. Which statement must be true?