If P → Q (P entails Q)

Then: P is true ⇒ Q must be true

Entailment Questions

Structure: Set of facts (no argument)

Task: What must be true?

Standard: 100% certainty

Assumption Questions

Structure: Argument with gap

Task: What's missing/required?

Standard: Logical necessity

Strengthen/Weaken

Structure: Argument to evaluate

Task: What affects validity?

Standard: Makes more/less likely

Must Be True Stems

• "If the statements above are true, which one of the following must also be true?"
• "Which one of the following must be true on the basis of the statements above?"
• "The statements above, if true, most strongly support which one of the following?"

Inference Stems

• "Which one of the following can be properly inferred from the passage?"
• "Which one of the following conclusions is most strongly supported by the information above?"
• "Which one of the following logically follows from the statements above?"

Properly Concluded Stems

• "Which one of the following can be properly concluded from the information above?"
• "The information above provides the most support for which one of the following?"
• "Which one of the following statements can be properly inferred from the passage?"

Critical Words to Note:

💡 Pro Tip:

The difference between "some" and "most" or "all" can completely change what you can infer. If the passage says "some lawyers are ethical," you cannot infer anything about most or all lawyers—only that at least one ethical lawyer exists.

Conditional Logic Rules

📚 Example:

Given: "If you study hard, you will pass the LSAT." (Study → Pass)

✓ Valid: If you didn't pass, you didn't study hard. (¬Pass → ¬Study)

✗ Invalid: If you pass, you studied hard. (Can't infer this!)

✗ Invalid: If you don't study hard, you won't pass. (Can't infer this!)

The Must Be True Standard:

⚡ Quick Test:

Try to create a scenario where the passage is true but the answer choice is false. If you can, it's not an entailment. If you cannot—no matter how hard you try—then it must be true.

💡 Important Caveat:

This is a general guideline, not an absolute rule! If the passage explicitly uses extreme language ("all candidates were rejected"), then an answer with extreme language ("no candidates were accepted") can be correct. Always verify against the passage.

Valid Combination Patterns:

⚠️ Common Mistake:

Don't combine statements that don't logically connect. If Statement 1 says "Some doctors are scientists" and Statement 2 says "Some scientists are wealthy," you CANNOT conclude "Some doctors are wealthy." The overlap might not exist!

Elimination Checklist:

• Eliminate if out of scope: Introduces concepts not mentioned in the passage
• Eliminate if too strong: Makes claims stronger than the passage supports
• Eliminate if contradictory: Conflicts with any passage statement
• Eliminate if merely possible: Could be true but not necessarily true
• Eliminate if requiring assumptions: Needs information beyond what's stated

🎯 Strategic Approach:

Aim to eliminate 4 answer choices, leaving you with 1. If you're stuck between 2 choices, look for which one makes a MORE conservative claim—that's usually the entailment. The LSAT rewards careful, conservative inferences over bold claims.

Passage:

About two million years ago, lava dammed up a river in western Asia and caused a small lake to form. The lake existed for about half a million years. Bones of an early human ancestor were recently found in the ancient lake-bottom sediments that lie on top of the layer of lava.

Question:

Which one of the following can be properly inferred from the passage?

Answer Choices Analysis:

✅ Key Takeaways:

• Read carefully: "lake-bottom sediments" means formed IN the lake
• Combine facts: Bones in lake sediments + lake no longer exists = bones deposited before drying
• Eliminate aggressively: Four answers made unjustified claims
• Conservative wins: The correct answer made a modest, well-supported inference

❌ Mistake #1: Confusing "Could Be True" with "Must Be True"

Many test-takers select answers that are merely consistent with the passage rather than logically guaranteed. Just because something is possible doesn't mean it must be true.

Solution: Ask "Is there ANY scenario where the passage is true but this answer is false?" If yes, eliminate it.

❌ Mistake #2: Adding Outside Knowledge or Assumptions

Your real-world knowledge or "common sense" can mislead you. Entailments must be based solely on what's stated in the passage.

Solution: Verify that every part of your answer is explicitly stated or directly inferable from the passage—nothing more.

❌ Mistake #3: Misreading Conditional Logic

Reversing or inverting conditional statements (mistaking P→Q for Q→P) is one of the most common logical errors on the LSAT.

Solution: When you see "if-then" statements, write out the contrapositive (¬Q→¬P) and check that carefully. Never assume the converse or inverse.

❌ Mistake #4: Ignoring Qualifiers

Missing words like "some," "most," or "only" can completely change the meaning and lead to incorrect inferences.

Solution: Circle or highlight quantifiers and modal terms as you read. Verify that answer choices preserve the correct qualifier strength.

❌ Mistake #5: Selecting Answers Based on Real-World Plausibility

An answer might seem "obviously true" in the real world but not be logically entailed by the passage. The LSAT tests logical reasoning, not general knowledge.

Solution: Base your answer solely on the passage, even if it describes an unusual or counterintuitive scenario. Accept the passage facts as given.

📖 Use Official LSAC Materials

The Law School Admission Council provides the only truly representative practice materials. Third-party questions often don't capture the nuance and precision of actual LSAT entailment questions.

🎯 Targeted Practice Approach

1. Drill by question type: Focus specifically on entailment/inference questions for 10-15 minutes daily
2. Untimed mastery first: Prioritize accuracy over speed initially—speed comes with practice
3. Analyze every answer: For each question, identify why the four wrong answers fail the "must be true" test
4. Track patterns: Note whether you struggle with conditional logic, quantifiers, or combining statements
5. Gradually add time pressure: Once you reach 90% accuracy untimed, practice with time constraints

💡 Advanced Practice Techniques

⏱️ Time Management

Aim for 60-90 seconds per entailment question once you're comfortable. These questions typically take slightly longer than some other types due to the need for precise analysis. Budget your time accordingly and don't rush—one careful read is better than two hurried ones.

🎯 High-Value Questions

Entailment questions appear 8-12 times per test across both Logical Reasoning sections. Mastering them provides consistent, predictable points toward your target score.

⚖️ Legal Reasoning Core

According to LSAC, "drawing well-supported conclusions" is essential to legal analysis. Lawyers must constantly determine what follows logically from statutes, precedents, and facts.

📈 Transferable Skills

The precision and logical rigor required for entailment questions improves your performance on assumption, strengthen/weaken, and flaw questions by sharpening your analytical skills.