Logical reasoning question types - Inference questions (must...

Learning Outcomes

After reading this article, you will be able to distinguish LSAT inference question types, specifically "must be true" and "most strongly supported" questions. You will understand how to deduce valid conclusions solely from provided evidence, avoid common reasoning errors, and use proven answer selection strategies to handle attractive but incorrect options. This knowledge is essential for success in the LSAT Logical Reasoning section.

LSAT Syllabus

For the LSAT Logical Reasoning component, you are required to identify logical inferences based exclusively on provided text. When revising this topic, focus on:

• recognizing LSAT “must be true” (inference) question types and how they differ from other question types
• evaluating answer choices using only information explicitly stated or deductively implied in the passage
• distinguishing between answers that "must be true" versus those that are only "possibly true" or unsupported
• applying process of elimination to remove answer choices that are too strong, too broad, or unsupported
• understanding reasoning chains, conditional statements, and structural indicators (quantity, contrast, etc.)

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, remember to look more closely at that area during your revision.

1. Which of the following is a correct inference question type on the LSAT?
   1. Which one of the following can be properly inferred from the information above?
   2. Which one of the following, if assumed, allows the conclusion to follow?
   3. Which one of the following best strengthens the argument?
   4. Which one of the following most undermines the argument?
2. Which answer choice best describes a valid approach to inference questions?
   1. Use real-world knowledge to inform your answer.
   2. Eliminate any answer not directly based on given information.
   3. Assume the most reasonable outcome.
   4. Choose the answer with the broadest scope.

3. True or false? A "must be true" answer could include information that is only suggested or likely, but not definitively proven by the passage.

4. What is the biggest danger when answering inference questions on the LSAT?

Introduction

Inference questions in LSAT Logical Reasoning require you to identify conclusions that are guaranteed by the passage. Unlike argument analysis or flaw spotting, inference questions ask: Based only on what is explicitly stated or logically required, what else must be the case? Answers must follow strictly from the stimulus. Real-world knowledge, assumptions, and what "seems likely" are not relevant. High performance depends on careful reading, attention to logical signals, and disciplined answer elimination.

Key Term: inference question
A question type that asks what must be true, or is most strongly supported, based solely on the facts provided in the passage or argument.

Types of LSAT Inference Questions

Inference questions are generally worded in one of two ways:

• "Which one of the following must be true?" (also seen as "can be properly inferred from the statements above?")
• "Which one of the following is most strongly supported by the passage?"

Both expect you to derive new information from the passage alone, but the emphasis differs:

• "Must be true" requires the answer to hold in every valid reading of the system.
• "Most strongly supported" allows answers that, while not certain, are overwhelmingly probable based on the evidence.

Key Term: must be true
Requires an answer choice that is a direct consequence of the stimulus; the answer cannot possibly be false if the stimulus is entirely true.

Key Term: most strongly supported
An answer that is not absolutely required, but is very strongly suggested or implied by the information provided—no other answer is better supported.

Recognising Inference Questions

LSAT inference questions often use the following stems:

• "If the statements above are true, which one of the following must also be true?"
• "Which of the following is most strongly supported by the information above?"
• "Which one of the following conclusions can be validly drawn from the passage above?"
• "Which of the following can be properly inferred from the given information?"

When you see these phrases, do not try to predict a main point or flaw. Instead, focus on direct logical connections.

Key Term: premise
A statement or fact provided in the stimulus assumed to be true for the purpose of the question.

How to Approach Inference Questions

For LSAT inference questions:

1. Treat every piece of information given as if it is absolutely correct, regardless of whether it matches your real-world knowledge.
2. Use only what is in the passage. Do not make assumptions or bring in outside information—even if the subject matter is familiar.
3. Pay careful attention to all qualifying language, such as "most," "some," "never," "at least," "often," or "except." These are clues to the logical range of valid inferences.
4. Look out for contrast or sequence indicators ("however," "in contrast," "additionally," "finally," "yet"), as these may structure the argument and affect what can be inferred.
5. Avoid being lured by answer choices that "sound reasonable." Stick to conclusions that are directly justified by the facts.

Worked Example 1.1

Passage:
"All new hires at the firm receive equipment training. Some employees in the IT department are new hires. All IT employees work on-site."

Question:
Which one of the following must be true?

A) All employees who receive equipment training work on-site.
B) Some employees who receive equipment training work in IT.
C) All IT employees are new hires.
D) Some on-site employees did not receive equipment training.
E) All new hires work in the IT department.

Answer:
B is correct. "Some employees in IT are new hires" and "all new hires receive equipment training" allow you to infer that "some IT employees receive equipment training." Since "all IT employees work on-site," those IT employees who are new hires also work on-site. Other options either introduce information not present in the passage, overgeneralise, or misrepresent logical links.

Valid Deductions and Eliminating Attractive Wrong Answers

To select the correct answer on an inference question, use the following process:

• Eliminate choices that introduce information not in the passage (out-of-scope).
• Eliminate answers that are too strong or "go beyond" what is logically required (often include words like "always," "never," "every").
• Eliminate answers based on assumptions, not facts.
• When two choices seem possible, prefer the answer that can be explicitly traced to the facts using deductive logic, rather than one that requires a leap.

Exam Warning

Many inference questions include answer choices that are tempting but only "possibly true", not "must be true". For "must be true" questions, possible is not enough—an answer must be certain.

Strong and Weak Language

Pay special attention to the strength of language used in answer choices:

• "Some" = at least one (safe, often correct inferences).
• "All," "always," "never" = must be 100% proven by text (can rarely be chosen unless the stimulus itself is categorical).
• "Most strongly supported" questions allow a result that is not definite but is overwhelmingly likely.

Revision Tip

For "must be true" questions, try to prove wrong each answer by creating a counterexample using only the given facts. If you cannot, the answer is usually correct.

Role of Conditional Logic

Many inference questions hinge on conditional ("if-then") reasoning.

If the stimulus states, "If X then Y," the contrapositive ("If not Y then not X") can also be validly inferred, but not necessarily the converse ("If Y then X").

Worked Example 1.2

Passage:
"If an athlete is selected for the national team, they must have a qualifying score. Ella is on the national team."

Question:
Which one of the following can be properly inferred?

A) Ella has a qualifying score.
B) All athletes with qualifying scores are on the national team.
C) No athlete can be selected without a qualifying score.
D) Only athletes aged over 18 can be on the national team.
E) All athletes with qualifying scores are also qualified coaches.

Answer:
A is correct. The conditional "If athlete is selected, they must have a qualifying score", and Ella is selected, so she must have a qualifying score. No information is given about age or coaching, and you cannot infer that having a qualifying score is sufficient for selection.

Most Strongly Supported Questions

These allow a conclusion that does not absolutely follow but is far better supported than any alternative.

Worked Example 1.3

Passage:
"Zara visits the gym after work every weekday when it is not raining. Last week, it rained most days."

Question:
Which one of the following is most strongly supported?

A) Zara never visits the gym on weekends.
B) Last week, Zara visited the gym less often than usual.
C) Zara always takes public transport to work.
D) Last week, it rained every day.
E) Gym attendance increases when it rains.

Answer:
B is correct. The statements support that Zara's gym visits are interrupted by rain, and it rained most days last week, so it is highly likely she went less often. Other choices are not supported or go beyond the facts.

Practice Approaches for Inference Questions

• Carefully read each answer choice and refer back to the passage after each elimination.
• Do not stop at an answer just because it "sounds plausible"—read all five choices fully.
• If down to two, prefer the weaker wording unless the passage justifies a stronger statement.

Summary

Key Point Checklist

This article has covered the following key knowledge points:

• Inference questions require valid deductions from stated facts only
• "Must be true" answers must directly follow; "most strongly supported" may be implied but not certain
• Real-world knowledge and outside assumptions must be ignored
• Overly strong language in answers is a key trap to be avoided
• Weak language ("some," "may") is often safer unless the passage supports a universal
• Conditional reasoning and contrapositives are frequently tested
• Eliminating out-of-scope or unsupported options is critical to success

Key Terms and Concepts

• inference question
• must be true
• most strongly supported
• premise