What is the difference between Must Be True and Most Strongly Supported questions?

Must Be True demands an answer the stimulus logically guarantees, with no gaps allowed. Most Strongly Supported lowers the bar slightly: the answer must be the most reasonable inference from the facts, even if it isn't a 100 percent airtight deduction. Treat both the same way in practice, prove each answer from the text, but allow a touch more flexibility on Most Strongly Supported when no answer is perfectly ironclad.

Can I use outside knowledge on Must Be True questions?

No. This is the single most common mistake. You must rely only on the statements in the stimulus. Real-world facts that feel obviously true are deliberately planted as wrong answers. If a conclusion requires anything beyond the words on the page, it is not the credited response.

Why is the correct answer often something I have to deduce by combining statements?

The test rewards reading for structure. Many Must Be True stimuli give you two or more conditional or factual statements that chain together. The credited answer typically links them, for example using one statement's conclusion as another's trigger, so a single surface-level read often misses it. Always ask whether two given facts combine into a new guaranteed truth.

LSAT Guides · Logical Reasoning

LSAT Must Be True Questions

Must Be True questions flip the usual Logical Reasoning relationship: instead of finding a flaw in the author's argument or an assumption holding it up, you accept everything the stimulus says as true and ask what follows from it. Your job is not to evaluate the reasoning. Your job is to be a detective who only states what the evidence guarantees.

That shift in mindset is the whole game. Strong test-takers treat the stimulus as a set of facts and refuse to add anything from the outside world. The correct answer is the one the passage forces you to conclude. Every wrong answer is something that merely could be true, sounds reasonable, or goes one inch beyond what the text proves.

How to recognize a Must Be True question

The question stem points downward, from the stimulus to the answer. You'll see phrasing like "If the statements above are true, which one of the following must also be true?" or "The statements above, if true, most support which one of the following?" The key signal is that the stimulus is treated as given and the answer must be derived from it.

Contrast this with assumption, strengthen, or flaw questions, where the stimulus is an argument you critique. Here there is often no argument at all, just a collection of claims, conditional statements, or data. Notice the difference between two close cousins: "must be true" demands airtight proof, while "most strongly supported" allows the answer to be a very reasonable inference rather than an absolute guarantee. Read the stem carefully so you know which standard applies.

The method: prove it from the text

Start by reading for structure, not persuasion. Catalog the hard facts and, crucially, the conditional statements. Conditionals are the engine of most Must Be True questions: if you're told "every chemist on the committee voted yes" and "Dr. Lee is a chemist on the committee," you can conclude Dr. Lee voted yes. You can also use the contrapositive, which is always valid: "if you did not vote yes, you are not a chemist on the committee."

Then evaluate each answer against a single test: can I point to the exact words in the stimulus that guarantee this? If you have to assume, estimate, or import common sense, the answer fails. Combine statements where they chain together, respect the direction of conditionals, and never reverse them. The right answer frequently combines two facts you were given separately, which is why a quick first read often misses it.

Common traps to avoid

The most seductive wrong answer is the one that's probably true in real life but not proven by the text. The LSAT loves to reward your outside knowledge with a wrong answer. Refuse it. A second classic trap reverses or negates a conditional improperly: from "if A then B," wrong answers offer "if B then A" or "if not A then not B," neither of which follows.

Watch for answers that are too strong, slipping in words like "all," "never," "only," or "must" when the stimulus only supported "some" or "can." Watch equally for scope shifts, where an answer swaps one term for a similar but distinct one. And beware the answer that simply restates one premise verbatim while ignoring the rest; sometimes that is the credited response, but more often the test wants you to combine, so verify it truly is forced rather than merely echoed.

A worked example

Suppose the stimulus reads: "Every novel shortlisted for the Maren Prize was published in the last two years. No book published by Oakhart Press has won the Maren Prize. The novel 'Tidewater' was published three years ago." The question asks what must be true.

Work the facts. From the first statement, anything published more than two years ago cannot be shortlisted, and you cannot win without being shortlisted. 'Tidewater' was published three years ago, so it was not shortlisted and therefore could not have won the Maren Prize. That is airtight, and an answer stating "'Tidewater' did not win the Maren Prize" must be true. Now reject the traps: "'Tidewater' was published by Oakhart Press" is unsupported, the Oakhart fact is a separate constraint never linked to this novel. "Every recent novel was shortlisted" reverses the conditional. "No novel published three years ago has ever won any prize" is far too broad. Only the proven statement survives.

This discipline, accept the facts and demand proof, is exactly what Argfluent's adaptive drills train into reflex; a few minutes on the free diagnostic will show you where your inferences drift beyond the text.

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Frequently asked questions

What is the difference between Must Be True and Most Strongly Supported questions?: Must Be True demands an answer the stimulus logically guarantees, with no gaps allowed. Most Strongly Supported lowers the bar slightly: the answer must be the most reasonable inference from the facts, even if it isn't a 100 percent airtight deduction. Treat both the same way in practice, prove each answer from the text, but allow a touch more flexibility on Most Strongly Supported when no answer is perfectly ironclad.
Can I use outside knowledge on Must Be True questions?: No. This is the single most common mistake. You must rely only on the statements in the stimulus. Real-world facts that feel obviously true are deliberately planted as wrong answers. If a conclusion requires anything beyond the words on the page, it is not the credited response.
Why is the correct answer often something I have to deduce by combining statements?: The test rewards reading for structure. Many Must Be True stimuli give you two or more conditional or factual statements that chain together. The credited answer typically links them, for example using one statement's conclusion as another's trigger, so a single surface-level read often misses it. Always ask whether two given facts combine into a new guaranteed truth.