LSAT Strengthen and Weaken

What It Is

Strengthen and Weaken questions ask you to find new external information that either bolsters or undermines the argument's conclusion. Unlike Flaw questions, the answers introduce new evidence not in the stimulus.

How to Identify the Question Type

• Which of the following, if true, most strengthens the argument?
• Which of the following, if true, most seriously weakens the argument?
• Which of the following would most support the argument above?

Strengthen: Look For

• A causal mechanism that explains why the correlation occurs
• Evidence eliminating the most obvious alternative explanations
• Confirmation that the sample or comparison is representative
• Data showing the relationship holds in similar contexts

Weaken: Look For

• An alternative explanation for the evidence presented
• Evidence that the correlation does not imply causation here
• Proof that comparison cases differ in important ways
• A counterexample that the conclusion fails to account for

Example Problem

Argument: 'City X installed red-light cameras and traffic accidents fell 30%. Therefore, red-light cameras reduce accidents.' Strengthen: Studies from other cities show similar accident reductions after camera installation. Weaken: City X also hired 200 more traffic officers during the same period.

The If-True Rule

Always accept the answer choice as true and ask only whether it helps or hurts the conclusion. Do not debate its real-world plausibility. The question tests your logical reasoning, not your outside knowledge.

Top Tips

• The correct answer must affect the specific conclusion, not just a premise
• For Weaken, you do not need to destroy the argument -- just make it less likely to be true
• Wrong answers often affect a side point rather than the main conclusion