Logical reasoning question types - Principle-justify-both an...

Learning Outcomes

After reading this article, you will be able to distinguish and approach LSAT 'principle-justify-both' and 'match-criterion' questions. You will learn how to apply abstract generalizations to arguments, identify when an answer justifies the reasoning or most closely conforms to it, and avoid common errors. You will develop efficient strategies to select the correct answer choice and confidently eliminate attractive distractors.

LSAT Syllabus

For the LSAT, you are expected to analyse arguments and abstract principles supporting them. You should focus your revision on:

• understanding how general principles function within LSAT logical reasoning questions
• differentiating between principle-justify-both (justify or strengthen) questions and match-criterion (conforming) questions
• selecting appropriate abstract criteria or rules that correctly strengthen or match the reasoning
• recognising and avoiding answer choices that are too broad, too narrow, or not logically connected to the argument
• applying principles to concrete LSAT-style examples and identifying the reasoning structure

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. A principle-justify-both question usually asks you to:
   1. Identify a general principle that, if valid, proves the conclusion.
   2. Find a flaw in the argument’s reasoning.
   3. Match wording from the premises.
   4. Provide a counterexample.

2. True or false? In a match-criterion question, the correct answer may present a rule broader than is needed for the argument.

3. Which of the following best describes a principle-match (conform) question?
   1. “Which one of the following principles, if valid, most helps to justify the argument above?”
   2. “Which one of the following principles most closely conforms to the reasoning above?”
   3. “Which of the following, if true, most strengthens the argument?”
   4. “Which answer solves the paradox above?”

4. What is a common exam trap in principle-justify questions?

Introduction

LSAT logical reasoning includes question types that focus on abstract principles instead of purely concrete facts. Two such question types are principle-justify-both (sometimes called "justify" or "strengthen with a principle" questions) and match-criterion (often phrased as "conform" or "most closely conforms") questions. Both demand that you identify and apply a general rule or criterion to an argument, but they differ in the nature of the logical connection required and the style of answer choice.

This article will explain how these question types work, the foundational logic, and the best strategies to approach them with accuracy and speed.

Principle-Justify-Both Questions

Principle-justify-both questions present an argument and ask you for a general principle that, if valid, guarantees or substantially supports the conclusion. These answer choices often take the form of an "if...then..." statement or a general rule. The principle must bridge the gap between the premises and the conclusion.

Key Term: principle-justify-both question
A question type that asks you to find a general rule—often abstract—that, if made valid, would support or strictly justify the argument's reasoning or conclusion.

Principle-justify-both questions often use prompts like:

• "Which one of the following principles, if valid, justifies the argument above?"
• "Which one of the following principles, if valid, most helps to justify the reasoning above?"

Your task is to find an abstract rule that turns the argument’s reasoning into a valid one, making the conclusion follow from the premises.

Match-Criterion (Conform) Questions

Match-criterion or match-principle questions ask you to identify which abstract principle among the answer choices most closely matches (conforms to) the argument’s pattern or reasoning. The criterion typically aligns with, but does not always directly justify, the argument.

Key Term: match-criterion question
A question that requires you to select a general principle or rule that most closely matches or conforms to the line of reasoning, method, or rule implicitly used in the argument or provided situation.

Match-criterion (conforming) questions often use stems such as:

• "Which one of the following principles most closely conforms to the reasoning above?"
• "The reasoning above most closely conforms to which of the following principles?"
• "Which of the following judgments best illustrates the principle stated above?"

Unlike justify questions, the correct principle in match-criterion questions matches the reasoning already found in the stimulus, rather than bridging a logical gap.

Key Differences and Strategies

• Principle-justify-both: The correct answer, if true, would guarantee or significantly bolster the conclusion. The connection is strong and often bridges a noticeable gap.
• Match-criterion: The correct answer mirrors the logic or generalizes the reasoning already present, but may not be required to guarantee the conclusion.

Identifying Correct Principles

The correct answer in principle-justify-both questions is:

• General enough to cover all uses of the reasoning.
• Narrow enough not to go beyond what is needed.
• Properly connects the evidence to the conclusion.

In match-criterion questions, the best answer will:

• Use similar logical structure or criteria as the given scenario.
• Not add assumptions or employ stricter requirements than found in the argument.
• Usually "fit" with the reasoning and outcome of the stimulus situation.

Key Term: abstract principle
A general rule stated in terms broad enough to apply to various specific cases, often expressed in “if…then…” or “whenever…must…” format.

Worked Example 1.1

Prompt: "No one should break a promise unless they have a very strong reason. Since Anita promised to help, she should only cancel if her reason is serious."

Which principle justifies this reasoning?

a) Breaking a promise is never acceptable. b) People should always help their friends. c) A promise should be broken only for a compelling reason. d) People must keep every commitment.

Answer:
Choice c) “A promise should be broken only for a compelling reason” is correct. This principle directly ties the evidence (“unless they have a very strong reason”) to the conclusion (“should only cancel if her reason is serious”). Choices a), b), and d) are too strict, off-topic, or do not match the balance in the argument.

Worked Example 1.2

Prompt: "It is wrong to punish everyone for the misdeeds of the few. The school’s decision to cancel the trip for all students because two broke rules is unfair."

Which principle conforms to the reasoning above?

a) Individuals should not be punished at all. b) Only guilty persons should be punished for their misdeeds. c) Punishment for wrongdoing should not be collective. d) Any group can be punished for one member's actions.

Answer:
Choice c) “Punishment for wrongdoing should not be collective” is correct. This captures the rule applied in the scenario. Choice b) is too narrow (focusing only on the guilty), while a) and d) do not match the context.

Structure and Traps

In principle-justify-both questions, incorrect answers are often:

• Too broad (e.g., banning promises for any reason).
• Too narrow (e.g., focusing on a case not matching the argument).
• Irrelevant (not addressing the logical gap).

In match-criterion questions, incorrect answers may:

• Restate just a fact or a detail in the scenario, not the principle.
• Apply a stricter or looser standard than used in the argument.
• Misrepresent the logic (focus on a different aspect).

Exam Warning

Principle questions sometimes offer answers that are worded similarly to the stimulus but do not match the logical structure. Always generalise the reasoning before you check answer choices. For justify questions, be wary of answers that seem to simply restate the conclusion or add new logic not present.

Revision Tip

For principle-justify-both, mentally “plug in” the answer choice: Does it force the conclusion to follow? For match-criterion, test if the answer could serve as the rule guiding the scenario exactly as stated.

Worked Example 1.3

Prompt: "If a person borrows an item, they must return it promptly. Since Sam hasn't returned the drill he borrowed, he has acted wrongly."

Which answer most closely conforms to the reasoning above?

a) Borrowing is wrong unless absolutely necessary. b) People must return borrowed items quickly or behave wrongly. c) Unreturned items are always lost forever. d) Only valuable items must be returned.

Answer:
Choice b) “People must return borrowed items quickly or behave wrongly” reflects the reasoning and outcome of the scenario. Choices a), c), and d) do not fit the specific pattern.

Summary

Key Point Checklist

This article has covered the following key knowledge points:

• Principle-justify-both questions require a general abstract rule making the argument valid or well-supported
• Match-criterion questions require identifying a rule or criterion that closely matches the argument’s logic or method
• The best answer in principle-justify must precisely bridge reasoning without unwarranted assumptions
• Match-criterion answers should use the same logical structure and degree of strictness as in the passage
• Common traps include choices that are too strict, too loose, or only vaguely similar to the reasoning in the question

Key Terms and Concepts

• principle-justify-both question
• match-criterion question
• abstract principle