LSAT Logical Reasoning: Inference

Rank 2 by frequency | 664 questions in corpus (14.7% of all questions)

An Inference question presents a set of statements (not necessarily an argument with a conclusion) and asks you to determine what can be logically concluded, inferred, or supported by those statements. The stimulus provides the evidence; you must find what follows from it. This is fundamentally different from argument-based questions – the stimulus is typically a fact set, not an argument to evaluate.

Your ability to draw valid conclusions from evidence, recognize logical entailments, combine multiple premises, distinguish between what must be true, what is likely true, and what could be true, and apply formal logic (conditionals, quantifiers, contrapositives).

The Task

Identify the one answer that is most strongly supported by, properly inferred from, or must be true given the information in the stimulus. The correct answer IS the conclusion – you must derive it.

What It Tests

Your ability to draw valid conclusions from evidence, recognize logical entailments, combine multiple premises, distinguish between what must be true, what is likely true, and what could be true, and apply formal logic (conditionals, quantifiers, contrapositives).

A. EXACT LOGICAL FLOW

Step-by-Step Stimulus Structure

1. No argument structure (typically): Unlike Flaw, Weaken, Strengthen, and Assumption questions, inference stimuli usually do NOT have a conclusion the author is trying to prove.

2. Fact set: The stimulus is a collection of statements, observations, data, or rules that the test-taker must treat as true.

How the "Conclusion" Relates to the Premises

There IS no conclusion in the stimulus. The correct answer IS the conclusion – it is the statement that logically follows from the given information. The test-taker must generate the conclusion rather than evaluate a given one. Support flows FROM the stimulus TO the correct answer.

The Nature of the Structure

The stimulus provides premises from which the test-taker must draw a valid inference. The standard varies by subtype: - Must Be True: 100% logically guaranteed - Most Strongly Supported: Best-supported conclusion, roughly 80% proven - Must Be False: 100% incompatible with the stimulus

How Correct vs. Incorrect Answers Are Designed

Correct answers either: 1. Directly restate information already in the stimulus (paraphrase) 2. Combine two or more facts to derive something new that is logically entailed 3. State the contrapositive of a conditional statement 4. Chain together conditional statements to produce a transitive inference

Incorrect answers: 1. Introduce information not found in or derivable from the stimulus 2. Are stronger than what the evidence supports 3. Propose unsupported relationships (causal, comparative, proportional) 4. Distort what the stimulus says 5. Reverse conditional logic

B. ALL WITHIN-TYPE VARIATIONS / SUBTYPES

Subtype 1: Must Be True (MBT)

The answer must be 100% logically guaranteed by the stimulus. No doubt or wiggle room permitted. - "If the statements above are true, which one of the following must also be true?" - "Which one of the following conclusions follows logically from the statements above?" - "Which one of the following can be properly inferred from the passage above?"

Subtype 2: Most Strongly Supported (MSS)

The answer need not be 100% certain; it must be the BEST-supported inference among the five choices. Approximately 80% – exceptions do NOT make the answer wrong. - "Which one of the following is most strongly supported by the information above?" - "The statements above, if true, would most strongly support which one of the following?" - "The statements above provide the most support for which one of the following conclusions?"

Subtype 3: Must Be False / Cannot Be True

The answer must be logically impossible given the stimulus information. 100% incompatible. - "If the statements above are true, which one of the following CANNOT be true?" - "Which one of the following, if true, would be most inconsistent with the information above?"

Subtype 4: Complete the Argument / Fill-in-the-Blank

The stimulus ends with a blank and the answer fills it in. Usually treated as MSS standard. - "Which one of the following most logically completes the passage?" - "Which one of the following best completes the argument?"

Subtype 5: Conditional/Formal Logic Inference

Contains explicit conditional statements (if-then). The correct answer is often the contrapositive or a chain of linked conditionals (A->B, B->C, therefore A->C).

Subtype 6: Quantifier-Based Inference

Contains quantified language (all, some, most, many, few, none). Key trap: "some" can include "all." Chaining: "All A are B" + "All B are C" = "All A are C." Limitation: "Most A are B" + "Most A are C" only proves "Some B are C."

C. ANSWER CHOICE CONSTRUCTION

How the Correct Answer Is Designed

Pattern 1 – Direct Restatement: Paraphrases a stimulus fact. When an answer accurately restates a passage fact, do not hesitate to select it.

Pattern 2 – Logical Combination: Combines two or more stimulus facts to produce a new statement. Often involves linking overlapping concepts, applying a general rule, or drawing the contrapositive.

Common Wrong Answer Patterns

1. Out of Scope / New Information: Introduces ideas not found in or derivable from the stimulus. ANY answer bringing in outside information should be eliminated.

2. Too Extreme / Stronger Than Support: Uses language stronger than the evidence supports ("always," "never," "all," "none"). Strongly worded statements rarely must be true unless the passage explicitly supports them.

D. COMMON PATTERNS AND TRAPS

Most Common Reasoning Structures in Stimuli

1. Conditional chains: Multiple if-then statements that can be linked 2. Quantifier overlaps: "Most," "some," "all" creating necessary overlaps 3. Comparative relationships: Comparing groups, quantities, or qualities 4. Definitional relationships: One concept defined in terms of another 5. Temporal/causal sequences: Events described in order with stated relationships 6. Disjunctive reasoning: "Either A or B" + "not A" = "B" 7. Contrapositive triggers: A conditional where the correct answer is the contrapositive

Common Traps

1. "Sounds right" trap: Matches real-world knowledge but isn't supported by the stimulus 2. Scope expansion trap: Stimulus discusses one group; answer extends to a broader group 3. Causal inference trap: Stimulus describes correlation; answer asserts causation 4. Quantifier shift trap: Stimulus says "some"; answer says "most" or "all" 5. Precision trap: Stimulus says "below B-minus"; wrong answer includes exactly B-minus

How LSAC Designs the Hardest Versions

1. Long, dense stimuli: Multiple facts hard to hold in working memory 2. Conditional logic requiring chaining: Multiple conditionals that must be combined and contrapositived 3. Quantifier interactions: Combining "most" and "some" where the inference is non-obvious 4. Disguised conditionals: "Unless," "only if," "whenever," "every," "without" 5. Multiple possible inferences: Several things could be inferred; must find the specific one in the answer choices 6. Subtle word choice in answers: Different wording from stimulus requiring recognition of logical equivalence

E. THE "ANATOMY" OF THE QUESTION

What Makes an Inference Stimulus Unique

  • No conclusion present: The stimulus is a fact set, not an argument
  • Everything is evidence: All statements treated as true
  • The answer IS the conclusion: Test-taker derives the conclusion rather than evaluating one
  • Support flows stimulus-to-answer: The stimulus supports the answer (contrast with Strengthen/Weaken where the answer supports/attacks the stimulus)

The Exact Cognitive Steps

1. Read the stimulus carefully and treat every statement as true evidence 2. Identify the subtype from the stem: MBT (100%), MSS (~80%), MBF, or Complete the Argument 3. Look for linkable concepts: statements that share terms and can be combined 4. Make a prediction before reading answer choices 5. For conditional stimuli: identify all conditionals, create contrapositives, look for chains 6. For quantifier stimuli: track exact strength ("all" vs. "most" vs. "some") – do not allow upgrades 7. Test each answer: "Does this HAVE to be true?" (MBT) or "Is this the BEST-supported statement?" (MSS) 8. For long stimuli: compare each answer with only the relevant portion (divide-and-conquer) 9. Use process of elimination: eliminate extreme, out-of-scope, and distorted answers first

How to Distinguish from Similar Types

  • vs. Necessary Assumption: Inference asks "What follows from these facts?" Assumption asks "What must be true for this argument to work?" Inference stimuli typically have NO argument; Assumption stimuli ALWAYS have one
  • vs. Identify the Conclusion: Main Conclusion asks you to identify the conclusion WITHIN the stimulus; Inference asks you to derive one NOT in the stimulus
  • vs. Sufficient Assumption: Sufficient Assumption gives an argument with a gap and asks what fills it; Inference gives facts and asks what follows

Official Content Examples

Example 1: Must Be True (Difficulty 4)

Source: PT9, Section 4, Question 13

Stimulus: "This summer, Jennifer, who has worked at KVZ Manufacturing for just over three years, plans to spend with her family the entire four weeks of paid vacation to which she is entitled this year. Anyone who has worked at KVZ Manufacturing for between one and four years is automatically entitled to exactly three weeks paid vacation each year but can apply up to half of any vacation time that remains unused at the end of one year to the next year's vacation."

Example 2: Most Strongly Supported (Difficulty 4)

Source: PT48, Section 4, Question 3

Stimulus: Since 1989, importing ivory from African elephants has been illegal in the US and Canada, but importing mammoth ivory remains legal. After the ban, imports labeled as mammoth ivory spiked. After a technique to distinguish the two was invented and its use became widely known, mammoth-labeled imports dropped dramatically.

Example 3: Logical Completion (Difficulty 2)

Source: PT65, Section 1, Question 4

Stimulus: "Swimming pools should be fenced to protect children from drowning, but teaching children to swim is even more important. And there is a principle involved here that applies to childrearing generally. Thus, while we should restrict children's access to the soft drinks and candies advertised on television shows directed towards children, it is even more important to teach them _______."

Example 4: Cannot Be True (Difficulty 4)

Source: PT29, Section 4, Question 22

Stimulus: A critic discusses Bach's chorale preludes and states: "Master artists never [create in order to express their own feelings], and Bach was a master artist."

Practice LSAT Logical Reasoning Questions