5.2 Weaken Questions
Key Takeaways
- Weaken questions ask for the statement that, if accepted as true, undermines the connection between the premises and the conclusion.
- Weakening an argument does not mean disproving the conclusion; it means demonstrating that the conclusion is less likely to follow from the given premises.
- In causal arguments, weaken choices introduce an alternative cause, show cause without effect, show effect without cause, or expose flawed data.
- Attacking the conclusion directly is a common mistake; effective weakeners target the logical gap or implicit assumptions connecting premise to conclusion.
- Distractor choices often strengthen the argument, address irrelevant background context, or attack an unstated claim not asserted in the stimulus.
Understanding Weaken Questions
Weaken questions are the conceptual flipside of Strengthen questions. On the LSAT, Weaken questions require you to adopt the perspective of a sharp, analytical skeptic. Your goal is to find the single answer choice that, if assumed true, casts the greatest amount of doubt on the author's conclusion.
Common stems include:
- "Which one of the following, if true, most seriously weakens the argument?"
- "Which one of the following, if true, casts the most doubt on the reasoning above?"
- "Which one of the following, if true, points to the most serious flaw in the researcher's plan?"
Like Strengthen questions, Weaken questions operate under the "if true" rule: you must accept the answer choices as factual assertions and evaluate their destructive force against the argument's logic.
The Anatomy of Logical Weakness
To weaken an argument, you do not attack the premises directly. On the LSAT, premises are treated as granted facts. Instead, you attack the inference—the unstated leap from premise to conclusion.
[ Premise / Evidence (Accepted Fact) ] + [ Weakening Counter-Fact ] ---X---> [ Conclusion (Reduced Probability) ]
A common misconception among test-takers is that a weakener must entirely refute or disprove the conclusion. In reality, a valid weakener merely renders the conclusion less probable or less justified than it was previously. If an answer choice makes you say, "Wait, if that is true, then the author's evidence might actually lead to a completely different outcome," that choice is a strong weakener candidate.
Five Core Patterns for Weakening Causal Arguments
Because causal arguments dominate Weaken sections, mastering causal weakening mechanics is essential. When an author claims $A \rightarrow B$, you can undermine the claim using five primary strategies:
| Weakening Strategy | Logical Mechanism | Example Scenario |
|---|---|---|
| 1. Alternative Cause ($C \rightarrow B$) | Introduces a third factor ($C$) that accounts for the observed effect ($B$). | Arguing that a reduction in heart disease was caused by new medications ($C$), not lower butter intake ($A$). |
| 2. Cause Without Effect ($A \text{ present}, B \text{ absent}$) | Shows a situation where the cause occurred, but the expected effect failed to materialize. | Demonstrating that another city adopted the identical tax rate ($A$) but experienced no business growth ($B$). |
| 3. Effect Without Cause ($B \text{ present}, A \text{ absent}$) | Shows that the effect occurred even when the alleged cause was completely absent. | Showing that patients recovered from the virus ($B$) without taking the experimental drug ($A$). |
| 4. Reverse Causation ($B \rightarrow A$) | Demonstrates that the direction of causality is backwards (the effect actually caused the cause). | Showing that depression causes lack of exercise, rather than lack of exercise causing depression. |
| 5. Flawed Data / Biased Survey | Demonstrates that the study, survey, or measurements used to infer causality were unrepresentative or flawed. | Revealing that a survey claiming 90% customer satisfaction polled only customers who renewed premium contracts. |
Weakening Non-Causal Arguments
When weakening arguments that do not rely on strict cause-and-effect claims, focus on these recurring vulnerability types:
1. Weakening Plan and Policy Arguments
To weaken a proposed plan, show that:
- The plan will trigger severe negative consequences that outweigh its benefits.
- An unaddressed practical obstacle prevents the plan from being implemented.
- The plan fails to address the root cause of the problem it intends to solve.
2. Weakening Sampling and Survey Arguments
To weaken an argument based on survey or study data, show that the sample is biased, unrepresentative of the broader population, or that respondents had incentives to lie.
3. Weakening Arguments by Analogy
To weaken an analogical argument, point out a critical, relevant difference between the two entities being compared that undermines the comparison.
Step-by-Step Tactical Method for Weaken Questions
- Read Question Stem: Confirm the target is to weaken or cast doubt.
- Identify Premises and Conclusion: Isolate the exact conclusion. Make sure you do not misidentify an intermediate claim as the main conclusion.
- Locate the Logical Vulnerability: Ask: "What is the author assuming here? What counter-explanation or missing factor is the author ignoring?"
- Prephrase the Weakening Strategy: For causal claims, prephrase an alternative cause or reverse direction.
- Evaluate Answer Choices: Select the choice that most directly reduces the likelihood of the conclusion.
Distractor and Trap Analysis
- The Strengthener Trap: An option that supports the conclusion. Under timed conditions, candidates often select an answer that feels logically connected to the argument, forgetting that they were asked to weaken it.
- Attacking a Stated Premise: Options that contradict a premise explicitly stated in the text. Remember: you must accept stimulus premises as true!
- Out of Scope Details: Information that touches on the general topic area but fails to affect the specific relationship between the premise and conclusion.
- Weak or Marginal Impact: Options that sound slightly skeptical but fail to significantly alter the probability of the conclusion when compared to a more devastating counter-fact.
A health analyst argues that eating a high-protein diet causes improved sleep quality, pointing to a survey showing that individuals who consume high-protein diets report 25 percent fewer sleep disruptions per night than those on low-protein diets. Which one of the following, if true, most seriously weakens the analyst's argument?
A tech company conducted a satisfaction survey among 500 customers who called customer service last month and found that 90 percent were highly satisfied. The company concluded that its customer service department provides excellent service to its overall customer base. Which one of the following, if true, most seriously weakens the company's conclusion?
A city plans to install automated speed enforcement cameras along its busiest downtown avenue to reduce vehicle-pedestrian collisions. The mayor argues that because driver speeding is involved in 60 percent of local collisions, installing speed cameras will significantly decrease pedestrian injuries. Which one of the following, if true, most seriously weakens the mayor's argument?
A corporate research team observed that branch offices that implemented flexible remote-work policies experienced a 20 percent increase in annual employee sales productivity compared to offices without remote work. The team concluded that allowing employees to work remotely increases sales productivity. Which one of the following, if true, most seriously weakens the research team's conclusion?