Strengthen &
Weaken

Master the art of identifying what strengthens or weakens an argument: the most frequently tested skill on the LSAT Logical Reasoning section.

LSAT Logical Reasoning

What Is an Argument?

Every LSAT stimulus presents an argument: a set of statements where one or more premises are offered as evidence for a conclusion. Before you can strengthen or weaken anything, you must first identify these two components clearly.

Premises

The facts, evidence, or reasons the author uses. They are presented as given.

Conclusion

The claim the author is trying to prove. Often signaled by words like "therefore," "thus," or "consequently."

The Gap in Every Argument

Almost every LSAT argument contains a gap: an unstated assumption that connects the premises to the conclusion. This gap is the target for both strengthen and weaken questions.

Recognizing Question Stems

Before reading the stimulus, always read the question stem first. This tells you whether to look for something that helps or hurts the argument.

Strengthen Stems

"Which of the following, if true, most strengthens the argument?" / "...provides the most support for..." / "...most justifies..."

Weaken Stems

"Which of the following, if true, most undermines the argument?" / "...most seriously weakens..." / "...casts the most doubt on..."

Anatomy of Strengthen

A correct strengthen answer does one of these things: it fills the gap between premises and conclusion, eliminates an alternative explanation, or provides additional evidence that supports the conclusion.

Anatomy of Weaken

A correct weaken answer does one of these things: it exposes the gap between premises and conclusion, introduces an alternative explanation, or provides a counterexample that undercuts the reasoning.

Strengthen vs. Weaken: Key Distinction

	Strengthen	Weaken
Goal	Make conclusion more likely	Make conclusion less likely
Targets	The gap / assumption	The gap / assumption
Correct answer...	Bridges the gap	Widens the gap
Degree needed	Doesn't have to prove	Doesn't have to destroy
Key word	"most strengthens"	"most weakens"

Common Argument Patterns

Recognizing the argument pattern helps you predict where the gap will be. Here are the four patterns that appear most often on strengthen/weaken questions:

Causal

X causes Y. Gap: maybe something else causes Y, or X and Y are correlated but not causal.

Analogical

A is like B, so what's true of A is true of B. Gap: A and B may differ in relevant ways.

Statistical

Sample shows X, so the whole population is X. Gap: the sample might not be representative.

Conditional

If P then Q. Gap: author may confuse necessary and sufficient conditions.

How to Apply the Method

1

Read the stem first. Determine whether you need to strengthen or weaken.

2

Identify the conclusion. Look for indicator words: "therefore," "thus," "hence," "it follows that," "must be that."

3

Identify the premises. What evidence supports the conclusion? Look for "because," "since," "given that."

4

Find the gap. What must the author be assuming? What's the logical leap?

5

Evaluate each choice. Ask: "Does this make the conclusion more or less likely?" Eliminate choices that are irrelevant to the gap.

Worked Example: Strengthen

Worked Example: Weaken

Advanced Example: Analogical Argument

This is an analogical argument: it assumes what worked in Country X will work in Country Y. The gap is that the two countries may differ in relevant ways.

To Strengthen

Show the countries are similar in relevant respects: "Country Y has a comparable tax structure, GDP, and industry mix."

To Weaken

Show a relevant difference: "Country Y's economy is driven by government spending, not private investment."

Spotting Trap Answers

The LSAT is designed to lure you into picking answers that feel relevant but don't actually affect the argument. Here are the most common traps:

1

Irrelevant comparison. The answer introduces a new topic that has no logical bearing on the argument's gap.

2

Opposite effect. A strengthen answer that actually weakens, or vice versa. Read the stem again before choosing.

3

Too extreme. Answers using "all," "never," or "always" often overshoot. Remember: you need "most strengthens," not "proves."

4

Restates a premise. A choice that merely repeats what's already stated doesn't strengthen or weaken anything new.

Common Mistakes

✕ Attacking the Premises

Premises are accepted as true. Don't pick an answer that says "the study was flawed" unless the argument itself questions the study.

✕ Confusing Strengthen/Weaken

Under time pressure, students pick a perfect weaken answer for a strengthen question. Always re-read the stem before selecting.

✕ Ignoring the Conclusion

The answer must affect the conclusion, not just relate to the topic. An interesting fact that doesn't impact the argument is wrong.

Summary: Your Toolkit

Step	Strengthen	Weaken
1. Find the gap	Same process	Same process
2. Predict the answer	What would bridge it?	What would widen it?
Causal argument	Rule out alternatives	Introduce alternatives
Analogical argument	Show similarity	Show key difference
Statistical argument	Sample is representative	Sample is biased
Conditional argument	Confirm the condition	Show condition unmet

Question 1 of 5

Argument: Employees at Trendale Corporation who participate in the company's wellness program have 30% fewer sick days than those who do not participate. Therefore, the wellness program is the primary reason for the reduced absenteeism among participants.

▼ Tap to read passage

Which of the following, if true, most weakens the argument above?

This is a causal argument. The correct answer introduces a selection bias: healthier people self-select into the program, so the program may not be causing the reduced sick days. This is a classic alternative explanation.

Question 2 of 5

Argument: Since the new recycling program was introduced in Springfield, the amount of waste sent to landfills has decreased by 15%. Clearly, the recycling program has been effective at reducing landfill waste.

▼ Tap to read passage

Which of the following, if true, most strengthens the argument?

By ruling out alternative causes, choice (B) bridges the gap. If no other initiatives were introduced, the recycling program is the most likely explanation for the decrease. Choice (A) actually strengthens the argument too, but less directly than (B).

Question 3 of 5

Argument: A survey of 200 customers at a luxury car dealership found that 85% were satisfied with their purchase. Therefore, most car buyers in the country are satisfied with their vehicles.

▼ Tap to read passage

Which of the following, if true, most weakens the argument?

This is a statistical argument. The gap is that the sample (luxury car buyers) may not represent the whole population (all car buyers). Choice (D) attacks the representativeness of the sample, which is exactly how you weaken a statistical argument.

Question 4 of 5

Argument: Country A reduced its carbon emissions by 25% after implementing a carbon tax. Therefore, Country B, which currently has no carbon tax, should implement one to achieve similar reductions.

▼ Tap to read passage

Which of the following, if true, most strengthens the argument?

This is an analogical argument. To strengthen it, you must show the two countries are similar in relevant respects. Choice (A) does exactly this by confirming that the key economic factors are comparable, making the analogy stronger.

Question 5 of 5

Argument: Students who eat breakfast perform better on standardized tests than students who skip breakfast. Therefore, schools should provide free breakfast programs because doing so will improve student test scores.

▼ Tap to read passage

Which of the following, if true, most weakens the argument?

The argument assumes breakfast causes better test performance. Choice (B) introduces a confounding variable: the real cause may be greater household academic support, not breakfast itself. Providing breakfast without that home support may not improve scores. This is a classic alternative-cause weakener.

Strengthen &Weaken

What Is an Argument?

The Gap in Every Argument

Recognizing Question Stems

Anatomy of Strengthen

Anatomy of Weaken

Strengthen vs. Weaken: Key Distinction

Common Argument Patterns

How to Apply the Method

Worked Example: Strengthen

Worked Example: Weaken

Advanced Example: Analogical Argument

Spotting Trap Answers

Common Mistakes

Summary: Your Toolkit

Question 1 of 5

Question 2 of 5

Question 3 of 5

Question 4 of 5

Question 5 of 5

Strengthen &
Weaken