Apply The
Principle

Master one of the LSAT's trickiest question types by learning to identify abstract rules and match them to new scenarios.

LSAT Logical Reasoning

What is a Principle?

On the LSAT, a principle is a broad, abstract rule or generalization that governs how things should work. Think of it as a universal guideline that applies across many different specific situations.

Principles often contain conditional language: "If X, then Y" or "One should always do Z when..." Recognizing this structure is the first step to mastering these questions.

The Two Directions

Principle → Application

You are given a general rule in the stimulus and asked which specific scenario in the answer choices conforms to or illustrates that rule.

Situation → Principle

You are given a specific scenario in the stimulus and asked which general principle in the answer choices best justifies or underlies the reasoning.

Why This Skill Matters

"Apply the Principle" questions appear 3 to 5 times on every scored LSAT section. They test your ability to move between abstract reasoning and concrete situations: a skill that is fundamental to legal analysis.

Anatomy of the Question

The Core Rule

Apply vs. Parallel Reasoning

	Apply the Principle	Parallel Reasoning
Stimulus	An abstract rule or generalization	A complete argument with premises and conclusion
Task	Find a scenario that fits the rule	Find an argument with the same logical structure
Focus	Content matching: do the facts satisfy each condition?	Structure matching: is the reasoning pattern identical?
Trap	Scenarios that match some but not all conditions	Arguments with similar topic but different logic

The 5-Step Method

1

Read the principle carefully. Identify every condition ("if..."), exception ("unless..."), and conclusion ("then...").

2

Translate into a formula. Write the principle as: "If [Condition A] and [Condition B], then [Conclusion], unless [Exception]."

3

Create a checklist. List every element the correct answer must satisfy.

4

Test each answer choice. Check whether each element of the principle is present. Eliminate any choice that fails even one element.

5

Confirm the match. The correct answer satisfies all conditions and reaches the same type of conclusion as the principle dictates.

Worked Example: The Promise Principle

Step 1: Identify the elements.

Condition

A person made a promise.

Conclusion

They must keep it.

Exception

Keeping it would cause serious harm to an innocent party.

Step 2: Our checklist. The correct answer must involve (1) a promise being made, (2) a judgment about keeping or breaking it, and (3) the presence or absence of serious harm to innocents.

Testing the Choices

A

"Lee promised to attend a meeting but decided not to because it was inconvenient." Fails: inconvenience is not serious harm. The principle says Lee should keep the promise.

B

"Sam forgot a promise to a coworker." Fails: forgetting is not a deliberate choice; the principle addresses whether one should keep a promise.

C

"Dana promised to deliver supplies but learned that doing so would endanger nearby residents. Dana did not deliver them." ✓ Matches all three elements.

D

"Jordan promised to repay a debt and did so." Partial: promise kept, but no mention of the harm element being relevant.

Harder Example: Dual Conditions

Translation: Justified regulation = safety concern AND no disproportionate burden. Both conditions are necessary.

✓ Correct Match

A ban on a toxic chemical (safety concern) that applies equally to all manufacturers (no disproportionate burden): justified.

✕ Tempting Trap

A noise ordinance (safety concern) that only affects one neighborhood's cultural festivals (disproportionate burden): not justified.

Negative Principles: When Not To

This principle tells us what someone should not do. The correct answer must show a situation where the condition is met (personal relationship exists) and the correct action follows (critic refrains from reviewing), or the condition is violated (critic reviews despite the relationship) and the answer identifies this as wrong.

Common Mistakes

✕ Partial Matching

Picking an answer that satisfies some conditions but ignores others. Every element of the principle must be accounted for.

✕ Reversing the Logic

Confusing "if A then B" with "if B then A." The principle's direction matters: conditions lead to conclusions, not the reverse.

✕ Topic Seduction

Choosing an answer because its topic sounds similar to the principle, even though its logical structure does not match.

Signal Words to Watch For

Word / Phrase	What It Signals	How to Handle It
"only if"	Necessary condition	This must be present for the conclusion to hold
"unless"	Exception / escape clause	Negate it and treat as "if not"
"should" / "ought to"	Prescriptive conclusion	Answer must show action aligned with this prescription
"whenever"	Sufficient condition (triggers every time)	If this is present, the conclusion automatically follows
"provided that"	Sufficient condition	Same as "if": meeting this guarantees the result

Quick Reference Summary

Step	Action	Key Question
1. Read	Identify conditions, conclusion, exceptions	What is the rule actually saying?
2. Translate	Rewrite as "If ... then ... unless ..."	Can I state this as a formula?
3. Checklist	List all required elements	How many boxes must be checked?
4. Eliminate	Test each choice against every element	Does this choice fail any condition?
5. Confirm	Verify the last standing choice satisfies all	Does every element truly match?

Question 1 of 5

Principle: "A teacher should give a student an extension on an assignment only if the student provides documentation of an emergency and the extension does not give that student an unfair advantage over classmates."

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Which of the following situations most closely conforms to the principle above?

Choice B satisfies both conditions: the student provides documentation (hospital note) and the extension does not create an unfair advantage (it is available to the entire class). Choice C has documentation but creates an unfair advantage. Choice A lacks documentation. Choice D denies the extension despite documentation.

Question 2 of 5

Principle: "A company should recall a product if there is credible evidence that it poses a health risk, even if the recall would be financially costly."

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Which of the following judgments most closely conforms to the principle?

Choice C is correct: there is credible evidence (independent lab confirmation) of a health risk (bacterial contamination), and the company recalls despite financial cost. Choice A lacks credible evidence. Choice B violates the principle by refusing to recall despite credible evidence. Choice D involves a cosmetic defect, not a health risk.

Question 3 of 5

Principle: "A journalist should not publish information obtained from a confidential source unless the information is of significant public interest and cannot be verified through any other means."

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The principle, if accepted, would most strongly support which of the following judgments?

Choice D is correct: the information is of significant public interest (government corruption affecting millions) and cannot be verified through other means (no public records). Choices A and C fail the "cannot be verified otherwise" condition. Choice B fails the "significant public interest" condition.

Question 4 of 5

Principle: "An employer is justified in terminating an employee only if the employee has been given clear prior warning about the problematic behavior and has failed to improve within a reasonable period."

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Which of the following situations most closely conforms to the principle?

Choice A is correct: the employee received clear prior warning (two written warnings) and failed to improve over a reasonable period (three months). Choice B lacks prior warning. Choice C also lacks any warning. Choice D fails because the employee did improve.

Question 5 of 5

Principle: "A city should approve a new development project only if the project includes adequate green space, addresses traffic impact, and receives majority support from the affected neighborhood."

▼ Tap to read passage

Which of the following judgments is most consistent with the principle?

Choice B is correct: the project fails one of the three required conditions (majority neighborhood support), so the city is justified in rejecting it. The principle requires all three conditions. Choices A, C, and D each approve a project that is missing at least one required element, violating the principle.

Apply ThePrinciple

What is a Principle?

The Two Directions

Why This Skill Matters

Anatomy of the Question

The Core Rule

Apply vs. Parallel Reasoning

The 5-Step Method

Worked Example: The Promise Principle

Testing the Choices

Harder Example: Dual Conditions

Negative Principles: When Not To

Common Mistakes

Signal Words to Watch For

Quick Reference Summary

Question 1 of 5

Question 2 of 5

Question 3 of 5

Question 4 of 5

Question 5 of 5

Apply The
Principle