Weakening Arguments

TL;DR

To weaken an argument, you need to attack the connection between the premise(s) and the conclusion, making the conclusion less likely to follow. Don't just contradict a premise or attack the conclusion directly; instead, focus on undermining the author's reasoning. Look for new information that introduces an alternative explanation, shows a flaw in the evidence, or highlights an overlooked factor.

1. The Mental Model

Think of an argument as a bridge connecting some starting points (premises) to a destination (conclusion). To weaken it, you don't need to blow up the bridge (destroy a premise) or block the destination (deny the conclusion); you just need to make the bridge shaky, so you're less confident it can get you to the conclusion.

2. The Core Material

Weakening arguments on the LSAT is all about finding the answer choice that makes the conclusion less probable, given the premises. You're looking for something that introduces doubt into the author's line of reasoning.

Here's the general process:

1. Identify the Conclusion: What is the author trying to convince you of? This is the central claim.
2. Identify the Premises: What evidence or reasons does the author provide to support the conclusion?
3. Identify the Gap/Assumptions: How does the author get from the premises to the conclusion? What unstated ideas or connections must be true for the argument to hold? Weakening questions often target these assumptions.
4. Find the Weakener: Look for an answer choice that attacks the link between the premises and the conclusion.

How Weakening Works:

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• Introduce an Alternative Cause: If the argument attributes an effect to a specific cause, a weakener might suggest another plausible cause for that same effect.
• Show a Flaw in the Evidence: The premises might be true, but perhaps they don't actually support the conclusion as strongly as the author implies.
• Challenge a Generalization: If the argument moves from specific examples to a general conclusion, a weakener might show that the examples aren't representative.
• Highlight Overlooked Factors: The argument might ignore something important that could change the outcome or explanation.
• Attack the Sufficiency of the Evidence: The premises might be necessary, but are they enough to prove the conclusion?

Let's visualize the core idea:

graph LR
    A["Premise 1"] --> C["Conclusion"]
    B["Premise 2"] --> C

    W["Weakener: Attacks the link/assumption"]

    A -- "Author's Reasoning/Assumption" --> C
    B -- "Author's Reasoning/Assumption" --> C

    W -- "Undermines Connection" --> C

In the diagram, the weakener doesn't deny Premise 1 or Premise 2, nor does it necessarily say the Conclusion is false. Instead, it makes the "Author's Reasoning/Assumption" less solid, therefore making the Conclusion less likely to be true based on those premises.

What NOT to Do:

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• Don't just deny a premise: If the author says "All birds have feathers," don't pick an answer that says "Some birds don't have feathers" unless the question explicitly allows for challenging premises (which is rare for weaken questions). Assume premises are true.
• Don't attack the conclusion directly: Just saying the conclusion is false doesn't weaken the argument; it just states an opposing view. The goal is to show why the author's reasoning for their conclusion is flawed.
• Don't pick an answer that strengthens the argument: Read carefully!
• Don't pick an answer that is irrelevant: The answer must have an impact on the argument presented.

3. Worked Example

Argument: "Studies show that children who regularly eat breakfast perform better in school than children who frequently skip breakfast. Therefore, schools should implement mandatory breakfast programs to improve students' academic performance."

Conclusion: Schools should implement mandatory breakfast programs to improve students' academic performance.
Premise: Children who regularly eat breakfast perform better in school.

Implicit Assumption/Gap: The argument assumes that the lack of breakfast is the cause of poor academic performance, and that providing breakfast will directly solve this. It also assumes that students who currently skip breakfast will benefit in the same way as students who already eat breakfast.

Which of the following, if true, most weakens the argument?

A) Many schools already have optional breakfast programs. (Irrelevant to the causal link)
B) Children who regularly eat breakfast often come from families that also provide a stimulating home environment and emphasize academic achievement. (This is a strong candidate!)
C) Some studies show that eating too much sugar for breakfast can negatively affect concentration. (Might weaken the type of breakfast, but not the core causal link the argument relies on).
D) Teachers report that students are often too sleepy to focus, regardless of whether they've eaten breakfast. (Doesn't directly attack the link between breakfast and performance).
E) Implementing mandatory breakfast programs would be expensive for schools. (Irrelevant to the academic performance claim).

Explanation:
Answer B most effectively weakens the argument. It introduces an alternative cause for the correlation. If children who eat breakfast also have other advantages (like a stimulating home environment), then it might be these other factors, not just breakfast itself, that are responsible for their better academic performance. Therefore, simply providing breakfast to all students might not yield the same academic improvements if those other factors are absent. This makes the conclusion that mandatory breakfast programs will improve academic performance much less certain.

4. Key Takeaways

• Always identify the conclusion first; it's what you're trying to undermine.
• Weakening means attacking the connection between premises and the conclusion, not the premises themselves.
• Look for alternative explanations or overlooked factors that could explain the phenomenon.
• Be wary of answer choices that are irrelevant, strengthen the argument, or merely contradict a premise.
• The correct answer makes the conclusion less likely to follow from the premises.
• Focus on the author's line of reasoning and its potential vulnerabilities.

5. Now Try It

Find an LSAT Weakening question from a practice test. Spend 15 minutes analyzing it. First, identify the conclusion and premises. Then, think about the unstated assumptions linking them. Finally, evaluate each answer choice to see which one most directly attacks that link or assumption, making the conclusion less compelling. Your success will be measured by your ability to clearly articulate why your chosen answer weakens the argument better than the others, focusing on the argument's internal logic.