Weaken questions ask which new fact, taken as true, does the most damage to the argument. Note what they don't ask: you're not looking for a fact that disproves the conclusion or contradicts a premise. You're looking for the fact that makes the evidence a worse reason to believe the conclusion.
That distinction is the whole game. Premises are fixed, the test won't reward you for fighting them. The vulnerability is always the inference: the alternative cause the author ignored, the biased sample behind the survey, the change between past evidence and future prediction. Weaken answers attack the bridge, not the pillars.
Weaken questions are frequent, usually three to five per test, and they're the purest test of the gap-spotting skill that runs through the entire assumption family. Students who prephrase the vulnerability before reading choices report the biggest accuracy gains on this type.
Stem language that signals this type:
Take every premise as given. The right answer makes the conclusion less likely even while all the stated evidence remains true. If your favorite answer works by contradicting a premise, it's wrong.
Before the choices: what would scare the author? For causal claims, a rival cause or reversed direction. For studies, a sampling or measurement problem. For predictions, a relevant difference between then and now.
Alternative cause, reverse causation, cause without effect, effect without cause, or a third factor driving both. One of these five shapes is the correct answer on most causal weaken questions.
"Most weakens" is comparative. An answer that merely opens a credible alternative explanation beats four answers that do nothing, even if the argument survives in weakened form.
An original question written in the LSAT style, not from a real test.
Office manager: After we switched the sixth floor to standing desks, sick-day usage on that floor fell by twenty percent. Standing desks evidently improve employee health, so we should install them on every floor.
Which one of the following, if true, most weakens the manager's argument?
Pick an answer to check your reasoning.
The right weaken answer often introduces brand-new information, so "that wasn't mentioned" is not an elimination reason. The real test is impact on the conclusion, not topical overlap.
Answers frequently damage a side issue, the practicality of a proposal, the motive of a speaker, while the actual conclusion walks away untouched.
Under time pressure it's shockingly easy to pick the answer that helps the argument. Re-read the stem on your final pass: are you weakening or strengthening?
Take the free diagnostic to see exactly where your points are going, or talk it through with a 170+ tutor, free, for 15 minutes.
No, premises are taken as true. Correct weaken answers leave every stated fact intact and instead break the link between those facts and the conclusion, usually by supplying an alternative explanation or exposing a flawed comparison.
It only has to damage the argument more than the other four choices. Introducing one credible rival explanation is routinely enough.
Because new information is exactly how you undermine an inference. Train yourself to evaluate impact on the conclusion rather than whether the topic appeared in the stimulus.
The five standard attacks: alternative cause, reverse causation, cause present without the effect, effect present without the cause, or a third factor causing both. Most correct answers are one of these.
Pick the new fact that makes the conclusion more believable.
Name the specific error in the argument's reasoning.
Find the unstated premise the argument can't live without.
Or head back to all question types · What is the LSAT?
Last updated July 9, 2026 · by the theLSATguru team