Weaken Questions
The argument looks solid. Your job is to crack it.
Two tools pair with this method. The miss-pattern analyzer shows which question types cost you the most points, and the blind review worksheet gives you a second pass at every miss.
What the question asks
The question asks which answer most weakens the argument. The stem says something like "Which one of the following, if true, most seriously weakens the argument?"
The new fact does not have to disprove the conclusion. It has to damage the reasoning. If the evidence no longer supports the conclusion well, the argument is weaker.
Step-by-step method
- Find the conclusion and the evidence. Separate what the author claims from what the author offers as proof. The weak spot is between them.
- Find the hidden assumption. Ask what must be true for the evidence to prove the conclusion. That assumption is your target.
- Predict the attack. Say what kind of fact would break the link. Three favorites: an alternate cause for the evidence, a skewed or tiny sample, or a fact showing the evidence is unreliable.
- Pick the choice that matches. The right answer makes the conclusion less likely to follow from the evidence. Partial damage counts. You do not need a knockout.
Worked examples
Both examples are original. They are not real LSAT questions.
Example 1
After the town imposed a curfew, vandalism fell by half. The curfew clearly worked.
Which one of the following, if true, most weakens the argument?
The answer: Vandalism also fell by half in nearby towns that imposed no curfew.
Why: If vandalism fell everywhere, the curfew may not be the cause. Some wider factor could explain both drops. The evidence no longer points at the curfew.
Example 2
Our survey shows 90 percent of readers love the new layout. Readers clearly prefer it.
Which one of the following, if true, most seriously weakens the argument?
The answer: The survey was sent only to subscribers who had already praised the redesign.
Why: A skewed sample tells you nothing about all readers. If only fans were asked, the 90 percent figure is meaningless. The evidence collapses.
Attack the link, not the facts
The premises of an argument are given. You cannot weaken an argument by denying its evidence, because the question treats the evidence as true. Your target is always the step from evidence to conclusion: the part the author filled in without saying.
That means the best weakeners usually introduce one new fact that makes the evidence point somewhere else. The argument says sales rose after the ad campaign, so the campaign worked. A choice that says a competitor closed its stores the same month does not deny the sales numbers. It breaks the link between the numbers and the conclusion. That is a weakener.
Watch out for choices that are merely consistent with the argument. A weakener must be hard to square with the reasoning. If the new fact could be true while the argument stays perfectly intact, it weakens nothing. The test is friction: does this new fact make the conclusion harder to believe?
Common traps
- A choice that weakens a side claim instead of the main reasoning. Aim at the link, not the scenery.
- A choice that attacks the topic rather than the argument. Disliking the conclusion is not weakening.
- A choice that is consistent with the argument. If it can be true alongside the reasoning, it weakens nothing.
- A choice that strengthens. Again: read the stem twice.
Practice the method
The free diagnostic scores every LR question type and shows exactly where you are losing points.