Last updated July 07, 2026 · Reviewed by the AnvayaPrep team
Introduction
Strengthen and Weaken Questions are among the most frequently tested question types on the LSAT, together accounting for approximately 20 to 25 percent of all Logical Reasoning questions. Strengthen questions ask for new information that makes the argument's conclusion more likely to be correct. Weaken questions ask for new information that makes the conclusion less likely. Both question types require identifying the argument's logical gap and determining what additional evidence would affect that gap.
This unit's 44 topics span the complete range of tasks: identifying what strengthens or weakens different argument types (causal, analogical, statistical, experimental, predictive, conditional, recommendation-based), recognizing and evaluating answer traps (irrelevant answers, opposite answers, out-of-scope answers, too-strong or too-weak answers), distinguishing strengthen from justify and weaken from flaw, developing pre-phrasing strategies for both question types, applying scope analysis to weaken questions, and mastering magnitude evaluation (determining which answer strengthens or weakens more).
The central insight of this unit is that strengthen and weaken questions are fundamentally about assumptions. The best strengtheners typically provide evidence for the argument's assumptions. The best weakeners typically attack or undermine those assumptions. This is why assumption mastery pays dividends here: once you identify what an argument assumes, you can reliably predict what would strengthen or weaken it.
Learning Objectives
- Identify what the argument concludes and where its logical gap lies before reading answer choices.
- Pre-phrase the characteristics of a strengthening or weakening answer based on the argument's gap.
- Apply argument-type-specific strategies for causal, analogical, statistical, experimental, and predictive arguments.
- Evaluate the magnitude of a strengthening or weakening effect to choose the answer that most strengthens or most weakens.
- Recognize and eliminate the most common wrong answer traps: irrelevant information, opposite-direction answers, out-of-scope answers, and answers that address the wrong part of the argument.
- Distinguish between strengthening an argument and justifying it: strengthening makes the conclusion more probable; justifying guarantees it.
- Apply scope analysis to weaken questions to verify that the weakening answer attacks the specific conclusion, not a different or broader claim.
High-Yield Concepts
| Argument Type | How to Strengthen | How to Weaken |
|---|---|---|
| Causal argument | Confirm causal mechanism; rule out alternative causes; show correlation is not coincidental | Provide an alternative cause; show reverse causation; introduce a third variable |
| Analogical argument | Show the two cases are similar in the relevant ways; eliminate important differences | Show a relevant difference between the two cases that undermines the comparison |
| Statistical argument | Show the sample is representative; confirm the data collection method is sound | Show the sample is biased or unrepresentative; challenge the measurement method |
| Experimental argument | Confirm controls were adequate; show the comparison group was appropriate | Show a confound variable; reveal that the experimental and control groups differed systematically |
| Predictive argument | Show the causal mechanism supports the prediction; confirm conditions are stable | Show conditions that prevent the predicted outcome; provide a contradicting precedent |
| Recommendation argument | Show the recommended action achieves the stated goal; show there are no better alternatives | Show the action will not achieve the goal; show significant negative side effects |
Pre-phrase before reading answer choices. After reading the argument, ask yourself: "If I were going to write the perfect answer to strengthen (or weaken) this argument, what would it say?" Your pre-phrase does not need to match the correct answer exactly, but it should identify the part of the argument you need to address. This eliminates at least two or three wrong answers immediately.
Study Strategy
Begin by mastering the fundamental insight: strengthen and weaken questions target the argument's assumptions. The best strengthener provides evidence for an assumption; the best weakener undermines it. This framing makes strategy more systematic.
Then study argument-type-specific patterns. Causal arguments are the most common type tested in strengthen and weaken questions, and they follow predictable patterns. Practice identifying causal gaps and predicting the three classic weakeners (alternative cause, reverse causation, third variable) until this is automatic.
Study the "magnitude" concept thoroughly. "Most strengthens" means you must choose the answer that has the largest positive effect on the argument's validity, not merely any answer that is relevant or consistent. Wrong answers in strengthen questions often do help a little but not as much as the correct answer.
Practice on EXCEPT variants (strengthen except, weaken except). These require identifying four answers that do have the stated effect and one that does not. Slow down on EXCEPT questions and verify each answer choice individually.
Strengthening an argument is like adding more load-bearing beams to a structure: it makes the structure more stable. Weakening an argument is like cutting a key beam: it makes the structure less stable. The best strengthener adds the most critical support; the best weakener removes the most critical support.
Common Mistakes
Selecting irrelevant answers. The most common wrong answer type presents information that is topically related to the argument but logically disconnected from the conclusion. Ask: "Does this answer affect the argument's conclusion?" If not, eliminate it regardless of how relevant it seems to the subject matter.
Selecting opposite-direction answers. Answer choices that strengthen appear as wrong answers in weaken questions, and vice versa. These are particularly dangerous because they address the argument's gap correctly, just in the wrong direction. When uncertain, verify which direction the answer pushes.
Confusing strengthen with justify. Strengthening makes the conclusion more probable. Justifying (sufficient assumption) guarantees the conclusion. Strengthen answers can be partial support. They do not need to prove the conclusion beyond doubt.
Confusing weaken with flaw. Weaken answers are new facts that damage the argument. Flaw answers describe what is already structurally wrong. On weaken questions, answer choices that describe the argument's reasoning pattern rather than providing new information are wrong.
Ignoring "most" in the question stem. "Most weakens" requires ranking effects. An answer that weakens a little and an answer that weakens substantially are both weakeners, but only one is the best answer. Always compare the potential impact of the final two or three candidates.
Exam Tips
After identifying the argument's conclusion and gap, mentally note what kind of argument you are dealing with: causal, analogical, statistical, or another type. This classification activates the relevant pattern of expected strengtheners and weakeners.
For weaken questions, the correct answer typically attacks the argument at its weakest point, which is usually the gap between the premises and the conclusion. Wrong answers often attack the premises themselves (making a true premise seem false) rather than the inference from premises to conclusion.
The "alternative cause" answer choice is one of the most common correct weakeners for causal arguments. If the conclusion claims A causes B, and an answer shows that C also causes B, the argument is weakened because C alone could explain B without A.
Do not select a weaken answer that attacks a premise rather than the inference. Strengthen and weaken questions ask you to assume all statements in the stimulus are true. Attacking the truth of a premise misreads the question type. The correct weaken answer provides new information (accepted as true) that makes the conclusion less likely despite the premises being true.
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