LSAT Must Be True Questions: Logical Reasoning Strategy, Examples & Tips

^{Last Updated: September 2026}

 

Must Be True questions are a fundamental LSAT Logical Reasoning question type. They test whether you can take a set of statements, accept the information provided, and determine which conclusion necessarily follows.

The key word is necessarily.

A correct answer is not merely plausible, reasonable, or consistent with the stimulus. It must be supported by the information given. If an answer could be false while every statement in the stimulus remains true, that answer cannot be the correct choice.

This distinction makes Must Be True questions particularly useful for developing the precise reasoning skills required throughout the LSAT.

Logical Reasoning is especially important on the current LSAT because the scored multiple-choice portion contains two Logical Reasoning sections and one Reading Comprehension section. For students preparing for law school, mastering inference questions therefore deserves significant attention.

 

What Is a Must Be True Question on the LSAT?

 

A Must Be True question asks you to identify a statement that follows logically from the information in the stimulus.

Typical question stems include:

• Which one of the following must be true?
• If the statements above are true, which one of the following must also be true?
• Which one of the following can be properly inferred?
• Which one of the following follows logically from the statements above?
• Which one of the following can be properly concluded from the information above?

 

These questions are generally considered part of the broader family of LSAT inference questions.

Unlike Strengthen, Weaken, Flaw, or Assumption questions, you are usually not being asked to evaluate whether an argument is persuasive. Instead, you are working with the information provided and identifying what follows from it.

For broader discussion of Logical Reasoning strategies, students can also visit the Top-Law-Schools LSAT Prep and Discussion Forum.

 

The Most Important Rule: Work Only With the Information Given

 

One of the most important habits you can develop for Must Be True questions is ignoring information that is not in the stimulus.

The LSAT requires test takers to answer Logical Reasoning questions based on the information provided rather than selecting a statement simply because it is true in the real world.

That means you should temporarily accept the stimulus on its own terms.

Suppose the stimulus says:

Everyone who works in Building A wears a blue identification badge. Maria works in Building A.

You may conclude:

Maria wears a blue identification badge.

You cannot conclude:

• Maria likes the color blue.
• Maria works for a large company.
• Maria is required to wear a suit.
• Maria has worked there for several years.

 

Any of those statements might happen to be true, but the stimulus does not establish them.

This leads to the central principle of Must Be True questions:

"Could be true" is not the same as "must be true."

 

A Simple Must Be True Example

 

Consider the following fictional example:

Every member of the university's appellate advocacy team is a law student.
Some members of the appellate advocacy team received scholarships.

What must be true?

Because every member of the team is a law student, and at least some team members received scholarships, we can conclude:

Some law students received scholarships.

Notice how little extra interpretation is required. The conclusion comes directly from combining the two facts.

We cannot conclude that:

• Most law students received scholarships.
• All law students participated in appellate advocacy.
• Only scholarship recipients joined the team.
• Students without scholarships could not join the team.

 

Each of those statements adds information that the stimulus never gave us.

 

How to Solve LSAT Must Be True Questions Step by Step

 

Step 1: Identify the Question Type

 

Read the question stem carefully before deciding what you are being asked to prove.

Words such as:

• must
• logically follows
• properly inferred
• properly concluded

 

usually indicate a strict inference task.

Once you recognize a Must Be True question, your mindset should be:

Which answer can I prove from the information given?

Do not ask which answer sounds most believable.

 

Step 2: Treat the Stimulus as a Set of Facts

 

On many Must Be True questions, it is more useful to think of the stimulus as information rather than as an argument you need to criticize.

Identify:

• categories,
• relationships,
• conditional statements,
• quantities,
• comparisons,
• sequences,
• and overlapping groups.

 

You are looking for connections between statements.

 

Step 3: Look for Facts That Can Be Combined

 

Many Must Be True questions are solved by combining two or more statements.

For example:

All patent attorneys at Firm X have technical backgrounds.
Some attorneys in Firm X's litigation department are patent attorneys.

Therefore:

Some attorneys in Firm X's litigation department have technical backgrounds.

No additional assumption is required.

 

Step 4: Make a Limited Prediction

 

Before becoming attached to an answer choice, ask yourself:

What can I safely conclude from this information?

Your prediction does not need to match the credited answer word for word.

The goal is simply to establish the boundaries of what the stimulus proves.

 

Step 5: Test Each Answer Choice

 

For each answer, ask:

Does this have to be true?

An even more useful test is:

Could this answer be false while everything in the stimulus remains true?

If the answer could be false without contradicting the stimulus, eliminate it.

This is one of the most reliable ways to distinguish a true Must Be True answer from a tempting answer that is merely possible.

 

Be Suspicious of Answers That Say Too Much

 

Correct Must Be True answers are often relatively modest.

Wrong answers frequently become attractive by taking a small amount of evidence and stretching it too far.

Watch for strong words such as:

• all
• always
• never
• only
• must
• completely
• exclusively
• none

 

Strong language is not automatically wrong. If the stimulus proves an absolute statement, an absolute answer may be correct.

But the stronger an answer is, the more evidence it requires.

Suppose the stimulus states:

Some associates at Firm A work remotely.

The following is supported:

At least one associate at Firm A works remotely.

The following is not supported:

Most associates at Firm A work remotely.

And this is certainly not supported:

All associates at Firm A work remotely.

The logical strength of the answer must match the logical strength of the evidence.

 

Conditional Reasoning in Must Be True Questions

 

Conditional reasoning appears frequently throughout Logical Reasoning and can be especially important in inference questions.

A basic conditional relationship looks like:

If A, then B.

Or symbolically:

A → B

Suppose:

If an applicant receives the scholarship, the applicant must submit an acceptance form.

This means:

Scholarship → Acceptance Form

If we know Elena received the scholarship, then we know Elena must submit the acceptance form.

 

The Contrapositive

 

From:

A → B

you can also conclude:

Not B → Not A

Using the scholarship example:

If an applicant does not submit the required acceptance form, that applicant cannot have satisfied the requirements associated with receiving the scholarship.

The contrapositive preserves the logical relationship.

 

What You Cannot Infer

 

From:

A → B

you cannot conclude:

B → A

This is known as reversing the relationship.

For example:

If someone is a federal judge, that person is a lawyer.

You cannot conclude:

If someone is a lawyer, that person is a federal judge.

Likewise, you cannot infer:

Not A → Not B

The failure to distinguish sufficient and necessary conditions is one of the most common sources of wrong answers in LSAT Logical Reasoning.

TLS forum discussions on conditional reasoning in Logical Reasoning provide additional student perspectives on recognizing when conditional relationships matter.

 

Quantifiers: All, Most, Some, and None

 

Must Be True questions frequently test whether you understand the exact meaning of quantity words.

 

All

 

All A are B.

This means every member of A belongs to B.

It does not mean every B is an A.

 

Some

 

On the LSAT, "some" means at least one.

Some lawyers are professors.

This establishes an overlap between lawyers and professors.

It does not tell us whether one lawyer, ten lawyers, or most lawyers are professors.

 

Most

 

"Most" means more than half.

If most members of Group A are members of Group B, you know there is substantial overlap, but you should not automatically convert "most" into "all."

 

None

 

No A are B.

This means the two categories do not overlap.

Understanding these distinctions becomes especially important when answer choices subtly change words such as "some," "most," and "all."

 

Example: Quantified Reasoning

 

Consider:

Every member of the law review editorial board is a second- or third-year law student.
Some members of the editorial board are third-year students.

Which statement must be true?

Some third-year law students are members of the editorial board.

That statement simply reverses the valid "some" relationship.

You cannot conclude:

Most third-year law students are members of the editorial board.

The stimulus tells us about the composition of the editorial board, not about the entire population of third-year students.

 

Common Wrong-Answer Traps

 

1. The "Could Be True" Answer

 

This is one of the most common traps.

The answer is compatible with the stimulus but is not required by it.

Ask:

Is this definitely established, or is it just possible?

If it is merely possible, eliminate it.

 

2. Outside Knowledge

 

Never choose an answer because you know it is generally true.

The LSAT is testing your reasoning from the provided information, not your knowledge of the subject matter.

A stimulus may discuss medicine, history, economics, science, law, or politics. You should not need specialized knowledge to answer correctly.

 

3. Reversed Logic

 

Stimulus:

If A, then B.

Trap answer:

If B, then A.

The reverse does not necessarily follow.

 

4. Confusing Necessary and Sufficient Conditions

 

Suppose:

Being admitted to Program X requires passing an entrance examination.

Passing the exam is necessary for admission.

It does not follow that everyone who passes the exam will be admitted.

There may be other requirements.

 

5. Extreme Language

 

If the stimulus says:

Some first-year students join study groups.

A trap answer might say:

All successful first-year students join study groups.

The conclusion is much stronger than the evidence.

 

6. New Information

 

A wrong answer may introduce a new idea that appears relevant but is never established.

If the stimulus discusses associate training, an answer about associate compensation may sound related. But unless compensation is addressed or logically implied, the answer is outside the scope.

 

7. Percentage and Number Confusion

 

Suppose:

A larger percentage of students at School A participate in clinics than at School B.

You cannot automatically conclude that more School A students participate in clinics.

School B may have a much larger student body.

Always distinguish percentages from absolute numbers.

 

Must Be True vs. Most Strongly Supported

 

These two question types are closely related, but they should not be treated as identical.

Question Type	What It Requires
Must Be True	The answer must follow necessarily from the facts in the stimulus.
Most Strongly Supported	The answer receives the strongest support from the information provided, even when the standard is somewhat less absolute.

 

Must Be True

 

A strict Must Be True answer must follow necessarily from the stimulus.

There should be no logically possible situation in which the stimulus is true and the credited answer is false.

 

Most Strongly Supported

 

A Most Strongly Supported question asks you to select the answer receiving the greatest support from the information provided.

A typical stem might say:

Which one of the following is most strongly supported by the information above?

For both types, staying close to the evidence is essential.

Students discussing this distinction on the TLS forums have similarly noted that strict Must Be True questions demand certainty, while "most strongly supported" wording can permit a somewhat less absolute inference. See the TLS discussion of Must Be True versus Most Strongly Supported questions.

 

Worked Example 1: Direct Inference

 

Consider:

All summer associates at Blackwood LLP attend an orientation program.
Jordan is a summer associate at Blackwood LLP.

What must be true?

Answer: Jordan attends the orientation program.

The reasoning is straightforward:

Summer Associate → Orientation

Jordan is a summer associate.

Therefore:

Jordan → Orientation

Nothing beyond the stimulus is required.

You cannot conclude that Jordan enjoys the program, receives an offer, works in a particular practice group, or eventually becomes an associate.

 

Worked Example 2: Combining Categories

 

Consider:

Every attorney in the firm's international arbitration group speaks at least one language in addition to English.
Some partners at the firm belong to the international arbitration group.

What must be true?

Answer: Some partners at the firm speak at least one language in addition to English.

The overlap between "partners" and "international arbitration group" allows us to carry the language requirement to those partners.

We cannot conclude that all partners are multilingual because we know nothing about partners outside the arbitration group.

 

Worked Example 3: Conditional Logic

 

Consider:

Anyone who chairs the hiring committee must be a partner.
Anyone who is a partner must have practiced law for at least six years.
David chairs the hiring committee.

We know:

Chair → Partner

and:

Partner → Six or More Years of Practice

Therefore:

Chair → Partner → Six or More Years of Practice

Because David chairs the committee, David must:

• be a partner; and
• have practiced law for at least six years.

 

This type of chained reasoning is common in inference questions.

 

Worked Example 4: Avoiding an Unsupported Inference

 

Consider:

Most students who participated in the school's moot court program reported that the experience improved their oral advocacy skills.

Which conclusion is justified?

A safe inference is:

More than half of the surveyed moot court participants reported improvement in their oral advocacy skills.

You cannot conclude:

Moot court participation improves the oral advocacy skills of every participant.

Nor can you conclude:

Students who did not participate in moot court have weaker advocacy skills.

Neither statement is established.

 

How to Improve at Must Be True Questions

 

Improvement requires more than completing large numbers of questions. You should also understand exactly why you missed them.

After reviewing a question, classify the mistake.

Did you:

• introduce outside information?
• reverse a conditional?
• overlook a contrapositive?
• confuse "some" and "most"?
• choose an answer that was merely possible?
• misread the scope of the stimulus?
• make a percentage-versus-number error?
• overlook a connection between two statements?

 

Keeping track of these patterns can reveal weaknesses that are more useful than simply counting how many questions you missed.

A long-running TLS discussion of LSAT study strategy and Logical Reasoning also emphasizes categorizing question types and carefully reviewing why particular answers fail.

 

Should You Diagram Every Must Be True Question?

 

No.

Diagramming is useful when the stimulus contains:

• several conditional statements,
• complex category relationships,
• formal logic,
• difficult quantifiers,
• or chains that are hard to track mentally.

 

For a simple inference question, writing out a full symbolic diagram may take more time than it saves.

The goal is not to diagram everything.

The goal is to recognize when a diagram makes the reasoning clearer.

 

Timing Strategy

 

Accuracy should come before speed while you are learning the question type.

At first:

1. Identify the question stem.
2. Read the stimulus carefully.
3. Determine what is provable.
4. Evaluate every answer choice.
5. Explain why four answers fail.

 

Once this process becomes automatic, speed usually improves naturally.

Trying to become fast before becoming accurate often reinforces bad reasoning habits.

 

How Must Be True Skills Help Beyond the LSAT

 

The ability to distinguish what evidence proves from what it merely suggests is useful well beyond standardized testing.

Law school routinely requires students to:

• separate facts from assumptions,
• identify what follows from precedent,
• interpret rules precisely,
• analyze competing arguments,
• and avoid conclusions that extend beyond the evidence.

 

Legal employers similarly value careful analytical reasoning, clear writing, and disciplined judgment.

Prospective and current law students who want to think beyond the LSAT can explore LawCrossing's guide to building a competitive law student career profile and its career-focused guide for aspiring attorneys.

Students who are beginning to think strategically about their longer-term direction may also find The Law Student Career Framework for Long-Term Success useful.

 

Frequently Asked Questions About LSAT Must Be True Questions

 

What does "Must Be True" mean on the LSAT?

 

It means the credited answer must logically follow from the information in the stimulus. If the answer could be false while all of the stimulus remains true, it is not a strict Must Be True answer.

 

Are Must Be True questions inference questions?

 

Yes. Must Be True questions are commonly grouped within the broader family of inference questions because they require you to derive a conclusion from information provided in the stimulus.

 

Can I use outside knowledge?

 

No. Base your answer on the information supplied by the question. Even accurate real-world knowledge can lead you away from the credited answer if the stimulus does not establish it.

 

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

 

A Must Be True answer must follow necessarily. A Most Strongly Supported answer receives the strongest support from the stimulus but may not always involve the same degree of logical certainty.

 

Should I diagram Must Be True questions?

 

Diagram when the stimulus contains conditional chains, overlapping categories, quantifiers, or other relationships that become easier to understand symbolically. Simple questions usually do not require it.

 

Why do I keep narrowing Must Be True questions to two answers?

 

Usually one answer is supported while the other is merely plausible. Apply the "Could this be false?" test to both choices. If one answer could be false without contradicting the stimulus, eliminate it.

 

What is the most common Must Be True mistake?

 

One of the most common mistakes is selecting a statement that could be true rather than one that must be true. Other common errors include reversed conditional reasoning and importing information that is not in the stimulus.

 

Final Takeaway

 

Must Be True questions reward disciplined reasoning.

You do not need to make the answer more complicated than the stimulus. Instead, focus on what the information actually proves.

Remember these core rules:

• Treat the stimulus as true.
• Stay within its scope.
• Combine statements only when logically justified.
• Watch the strength of words such as "some," "most," and "all."
• Do not reverse conditional relationships.
• Reject answers that merely could be true.
• Ask whether the answer could be false while the stimulus remains true.

 

If the answer could be false, it is not something that must be true.

As you become more precise about the difference between evidence and assumption, Must Be True questions often become one of the more manageable Logical Reasoning question types.

 

Related Top-Law-Schools Resources

 

• LSAT Prep and Discussion Forum
• Must Be True, Assumption, and Flaw Question Tips
• Logical Reasoning Strategy and Question Families
• Conditional Reasoning in Logical Reasoning
• Must Be True vs. Most Strongly Supported Discussion
• "Which of the Following Can We Properly Infer?" Discussion
• Improving Consistency on Logical Reasoning

 

Related LawCrossing Resources

 

• The Law Student Career Framework for Long-Term Success
• Building Career Clarity: A Practical Guide for Law Students
• The Law Student's Guide to Building a Competitive Career Profile
• Navigating Law School: A Career-Focused Guide for Aspiring Attorneys