Strict support, not plausibility
Test each answer choice by asking whether the stated facts, and only the stated facts, force it to be true. An answer that is merely consistent with the passage, or that most people would guess is probably true, is not the same as an answer the passage actually proves.
- Eliminate answers requiring outside knowledge or common sense not stated in the passage
- Eliminate answers that are broader or stronger than what the facts support
- Favor a narrow, modest answer over a sweeping one when both seem to fit
- Combine multiple stated facts if the question supplies more than one
Conditional chains: contrapositive only
Given 'if A, then B,' the only automatically valid restatement is the contrapositive: 'if not B, then not A.' Reversing the conditional ('if B, then A') or negating both sides ('if not A, then not B') are classic invalid moves that a wrong-answer choice will often exploit.
Chain several conditionals together only through their contrapositives, in reverse order, to find what a stated negation at the end of the chain forces at the beginning.
What LSAC says about drawing conclusions
LSAC lists drawing well-supported conclusions among the skills the Logical Reasoning section tests, and says each Logical Reasoning question asks about a short passage with one question or, rarely, two.
For practice material, LSAC says its Official LSAT TriplePrep series reflects the current design of the LSAT starting with the August 2024 administration, and that SuperPrep and SuperPrep II remain available as historical resources because they explain why each question has one correct answer and the others are incorrect.
3 original practice questions
Written for this guide, not taken from any licensed test. Your result is saved on this device only.
All members of the Riverside Book Club have read at least one novel by Toni Morrison. No member of the Riverside Book Club has read fewer than ten novels total. Which of the following must be true?
Answer and explanations
Correct answer: B. Combining both stated facts, any member has read ten or more novels total and at least one Morrison novel among them: exactly what this choice states. The other choices all overreach beyond what the two facts actually support.
If the museum extends its hours, attendance will increase. If attendance increases, the museum will need to hire additional staff. The museum has decided not to hire additional staff. Which of the following must be true?
Answer and explanations
Correct answer: A. This is a conditional chain: extend hours leads to more attendance leads to needing staff. Not hiring staff negates the final link, and chaining the contrapositives back through the sequence forces the first link's negation too: hours will not be extended.
Every student in Mr. Alvarez's class who submitted the extra-credit essay received a grade of at least a B on the final exam. Elena is in Mr. Alvarez's class and received an A on the final exam. Which of the following must be true?
Answer and explanations
Correct answer: B. The stated rule guarantees only a floor for essay-submitters and says nothing about non-submitters. An A is consistent with the rule either way, since the rule never excludes non-submitters from earning one: the other choices all assume more than the passage states.
Questions this guide answers
What does an LSAT inference question ask?
What must be true given only the stated facts, not what is plausible, likely, or supported by outside knowledge.
Why do sensible-sounding inference answers turn out wrong?
They usually need one extra assumption the passage never supplied. An answer merely consistent with the facts is not the same as one the facts actually prove.
What is the contrapositive rule for LSAT conditionals?
Given if A, then B, the automatically valid restatement is if not B, then not A. Reversing it or negating both sides is not valid.
Which conditional moves do wrong answers exploit on inference questions?
Reversing a conditional, so if B then A, or negating both sides, so if not A then not B. Neither follows from the original statement.
Should I choose the broad or the narrow inference answer?
Favor the narrow, modest answer the facts force when both seem to fit, and eliminate answers that are broader or stronger than the stated facts support.
How do I chain several conditionals on the LSAT?
Only through their contrapositives, in reverse order, so that a stated negation at the end of the chain shows what is forced at the beginning.
How many questions follow each Logical Reasoning passage?
One, or rarely two, according to LSAC's description of Logical Reasoning, so an inference must usually come from a handful of facts.
Which LSAC books match the current LSAT design?
The Official LSAT TriplePrep series, which LSAC says reflects the current design starting with the August 2024 administration.
Your next steps
- Ask 'does this have to be true' for every choice, not 'could this be true.'
- Chain conditionals only via contrapositive, never by reversing or negating both sides.
- Prefer the narrowest answer the facts actually force.
- Rule out any answer needing information the passage never gave.