Evaluate the
Argument

Master the art of identifying logical strengths and weaknesses in LSAT Logical Reasoning passages. Learn to spot hidden assumptions, assess evidence, and choose the best answer.

LSAT Logical Reasoning

What Does "Evaluate the Argument" Mean?

On the LSAT, "Evaluate the Argument" questions ask you to identify what additional piece of information would be most useful in determining whether an argument's conclusion is well-supported. You are not asked to strengthen or weaken: you are asked what would help you decide.

Anatomy of an Argument

Why This Skill Matters

Frequency

Evaluate questions appear on nearly every scored LSAT Logical Reasoning section: typically 1 to 3 per section.

Transferable

The same analytical thinking applies to Strengthen, Weaken, and Flaw questions: mastering evaluation boosts all four question types.

Efficiency

Once you find the assumption, you can eliminate wrong answers quickly. Most students spend too long because they skip this step.

The Core Principle

Think of the correct answer as a two-sided test. If the answer to the question is "yes," the argument gets stronger. If "no," it gets weaker (or vice versa). Wrong answers are one-sided or irrelevant: knowing the answer would not change your assessment of the argument.

The Yes/No Test

Evaluate vs. Strengthen vs. Weaken

	Evaluate	Strengthen	Weaken
Goal	Find what tests the argument	Find what supports the conclusion	Find what undermines the conclusion
Answer format	Often phrased as a question	A statement of fact	A statement of fact
Direction	Two-sided (yes/no)	One-sided (supports)	One-sided (attacks)
Key skill	Identify the assumption	Bolster the assumption	Attack the assumption

Step-by-Step Method

1

Identify the conclusion. What is the author trying to convince you of? Look for indicator words: "therefore," "thus," "so," "it follows."

2

Identify the premises. What evidence or reasons does the author give? Separate facts from the claim.

3

Find the gap (assumption). What must be true for the premises to logically lead to the conclusion? This unstated link is the target.

4

Apply the Yes/No test. For each answer, ask: "If the answer to this is yes, does the argument get stronger? If no, does it get weaker?" The correct choice passes this test.

5

Eliminate irrelevant choices. Any answer where knowing yes or no makes no difference to the argument is wrong.

Worked Example: The Bird Study

Premise

Urban birds sing at higher pitches than rural birds of the same species.

Conclusion

Urban noise pollution causes birds to raise their song pitch.

Applying the Yes/No Test

Which of the following would be most useful to know in order to evaluate the researcher's argument?

A

"Whether birds in urban parks also eat different food than rural birds" : Irrelevant to pitch and noise. Fails the test.

B

"Whether people enjoy hearing birds sing at higher pitches" : Totally irrelevant to the causal claim. Fails the test.

C

"Whether birds that are moved from rural to urban environments raise their pitch" : Yes = strengthens (the change in environment caused the change). No = weakens (the difference is genetic, not environmental). Passes both sides.

D

"Whether rural forests are quieter than urban parks" : This is already assumed by the stimulus. Knowing yes adds nothing new. Fails the test.

Worked Example: The New Policy

Premise

Scores rose 15% after the policy was introduced.

Conclusion

The flexible policy caused the rise.

Harder Example: The Historical Claim

Gap: "No evidence found" does not mean "no metal tools existed." The argument assumes absence of evidence is evidence of absence, and that the only explanations are "metal tools" vs. "fundamentally different techniques."

Common Mistakes

✕ Picking a Strengthener

A choice that only helps the argument (one-sided) is not an evaluator. It must cut both ways.

✕ Picking a Weakener

Similarly, a choice that only hurts the argument is a weakener, not an evaluator. Apply the yes/no test.

✕ Ignoring the Conclusion

Students often evaluate the premises' truth rather than whether the conclusion follows. Focus on the logical connection.

Recognizing Question Stems

Evaluate questions use distinctive language. Memorize these phrasings so you immediately know what type of question you are facing:

1

"Which of the following would be most useful to know in order to evaluate the argument?"

2

"The answer to which of the following questions would be most helpful in evaluating the reasoning above?"

3

"Which of the following would it be most important to know in assessing the truth of the conclusion?"

4

"Determining which of the following would be most useful in evaluating the force of the argument?"

Quick Reference Summary

Step	Action	What to Look For
1	Read the stimulus	Conclusion + premises
2	Identify the gap	What must be true (assumption)
3	Read the question stem	"Evaluate" / "useful to know"
4	Test each choice	Yes/No: does it cut both ways?
5	Eliminate and confirm	One-sided or irrelevant = wrong

Question 1 of 5

Passage: A city's parks department planted 500 new trees along major roads last year. This year, air quality measurements in those areas show a 10% improvement. The parks department claims that the tree-planting initiative is responsible for the improvement in air quality.

▼ Tap to read passage

Which of the following would be most useful to know in order to evaluate the parks department's claim?

If air quality also improved where no trees were planted (yes), then the trees are likely not the cause (weakens). If air quality did not improve elsewhere (no), the trees are more plausibly the cause (strengthens). This cuts both ways, making it the correct evaluator.

Question 2 of 5

Passage: Studies show that students who eat breakfast perform better on standardized tests than students who skip breakfast. Therefore, schools should provide free breakfast programs to improve test performance.

▼ Tap to read passage

The answer to which of the following would be most helpful in evaluating the reasoning above?

The argument assumes breakfast is the cause of better performance. If breakfast-eaters differ in other relevant ways (more sleep, higher income, more parental support), the correlation may not be causal (weakens). If they do not differ, breakfast is more likely the cause (strengthens). This is the classic confounding-variable evaluator.

Question 3 of 5

Passage: A pharmaceutical company tested a new drug on 200 patients with chronic headaches. After six weeks, 70% of participants reported fewer headaches. The company concluded that the drug is effective at reducing chronic headaches.

▼ Tap to read passage

Which of the following would be most useful to know in order to evaluate the company's conclusion?

If the placebo group also improved at 70% (yes), the drug had no special effect (weakens). If the placebo group did not improve (no), the drug likely worked (strengthens). This directly tests the causal assumption by checking for the placebo effect.

Question 4 of 5

Editorial: Our city's crime rate dropped 20% last year, the same year we increased the police budget by 30%. Clearly, the increased police funding is working to reduce crime.

▼ Tap to read passage

Determining which of the following would be most useful in evaluating the force of the editorial's argument?

If comparable cities also saw a 20% drop without extra police funding (yes), the budget increase may not be the cause (weakens). If those cities did not see a drop (no), the budget increase is a more plausible explanation (strengthens). This is a classic control-group evaluator testing alternative causes.

Question 5 of 5

Scientist: Deep-sea fish species discovered near hydrothermal vents have unusually high levels of heat-resistant proteins. Since no other known environmental factor in the deep sea would select for heat resistance, these proteins must have evolved specifically as an adaptation to the vents' extreme temperatures.

▼ Tap to read passage

Which of the following would be most useful to know in order to evaluate the scientist's reasoning?

If fish far from vents also have high heat-resistant proteins (yes), the proteins may serve another function, not vent adaptation (weakens). If they do not (no), the correlation between vent proximity and heat-resistant proteins supports the adaptation claim (strengthens). This directly tests the assumption that vents are the selective pressure.

Evaluate theArgument

What Does "Evaluate the Argument" Mean?

Anatomy of an Argument

Why This Skill Matters

The Core Principle

The Yes/No Test

Evaluate vs. Strengthen vs. Weaken

Step-by-Step Method

Worked Example: The Bird Study

Applying the Yes/No Test

Worked Example: The New Policy

Harder Example: The Historical Claim

Common Mistakes

Recognizing Question Stems

Quick Reference Summary

Question 1 of 5

Question 2 of 5

Question 3 of 5

Question 4 of 5

Question 5 of 5

Evaluate the
Argument