LSAT strengthen and weaken questions are among the most frequently tested Logical Reasoning question types, with weaken appearing approximately 254 times and strengthen about 196 times across analyzed tests. Both types share a common foundation: you must identify the argument's unstated assumption and then either support it or attack it. This guide breaks down the strategy for each type and shows you how to avoid the most common traps.
Strengthen adds support for the conclusion. Weaken undermines the argument. Both target the assumption.
| Feature | Strengthen Questions | Weaken Questions |
|---|---|---|
| Goal | Make the conclusion more likely | Make the conclusion less likely |
| Core skill | Identify and support the assumption | Identify and attack the assumption |
| Common stem language | Supports, strengthens, justifies | Undermines, weakens, calls into question |
| Correct answer does... | Closes the gap or adds support | Opens the gap or provides counter-evidence |
| Wrong answer trap | Answers that weaken instead | Answers that strengthen instead |
| Frequency | ~196 appearances (~7%) | ~254 appearances (~9%) |
Both target the assumption.
Conclusion is what the author claims. Premises are the evidence offered. The gap is what must be true but isn't stated.
The gap is what must be true but isn't stated.
Worked Example
A city installed speed cameras at 10 intersections last year. Accidents at those intersections decreased by 30%. The city council concludes that speed cameras reduce accidents.
Ask what would make the conclusion more likely. Look for answers that close the gap. Eliminate out-of-scope answers.
Eliminate out-of-scope answers.
Ask what would make the conclusion less likely. Alternative explanations are powerful weakeners. Counterexamples challenge the logic.
Counterexamples challenge the logic.
Worked Example
A pharmaceutical company argues that their new drug is safe because clinical trials showed no serious side effects over a 6-month period.
Answers that introduce irrelevant topics. Answers with always/never/must. Answers that do the opposite of what's needed.
| Wrong Answer Type | What It Looks Like | Why It's Wrong |
|---|---|---|
| Out of scope | Introduces a topic not in the argument | Does not affect the argument's logic |
| Too extreme | Uses always, never, must, all | Overstates the needed effect |
| Reversed effect | Strengthens when asked to weaken (or vice versa) | Does the opposite of what the question asks |
| Premise restater | Repeats evidence already in the argument | Does not add new information |
| Irrelevant comparison | Compares to unrelated situations | Does not address the specific argument |
Answers that do the opposite of what's needed.
Strengthen questions ask you to find new information that makes the conclusion more likely to follow from the premises. Weaken questions ask for information that makes the conclusion less likely. Both types require you to identify the argument's unstated assumptions.
Identify the conclusion and premises, then ask what must be true but is not stated for the conclusion to follow. The gap between what the premises prove and what the conclusion claims is the assumption. Correct answers for both types target this gap.
Combined, strengthen and weaken questions make up a significant portion of Logical Reasoning. Weaken questions appear approximately 254 times across analyzed tests, while strengthen questions appear about 196 times, making them among the top five most common types.
Common traps include out-of-scope answers that introduce irrelevant topics, answers with overly extreme language like always or never, answers that reverse the intended effect, and answers that only restate premises without adding new information.