Logical ReasoningDifficulty: Easy

PT103 S3 Q8 Explanation

Grasses and woody plants are planted

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsFlaw

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Stimulus

Grasses and woody plants are planted on dirt embankments to keep the embankments from eroding. The embankments are mowed to keep the grasses from growing too tall; as a result, clippings pile up. These piles of clippings smother the woody plants, causing their roots, which serve to keep the embankments from eroding, bringing in predators to eradicate the rodents will prevent erosion of the embankments.

What this question is testing

Flaw

Your task

Describe the reasoning error the argument actually commits.

Common trap

Answers that name a real logical flaw the argument doesn't actually make.

Winning move

Articulate the gap in the reasoning yourself, then match it to the choice that describes that gap.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
8.

Which one of the following is an error of reasoning in

Answer choices

  1. Bad Conclusion Match Not Causal Flaw5% picked this

    Two events that merely co-occur are treated as if one caused

    This answer refers to one of the 10 famous flaws, Causal Overconfidence, in which the author's conclusion is overconfidently assuming one causal explanation for why something has occurred / is occurring, when there are alternate explanations possible. This answer is specifically claiming that the argument presented a correlation between X and Y and then concluded that X causes Y. We can tell just by looking at the conclusion that this description doesn't match the argument. The author's conclusion isn't a causal explanation for something that's occurred / is occurring. It's a prediction. The prediction has a causal element to it (bringing in predators will cause erosion to be prevented), but the evidence didn't spotlight a correlation between predators and low-erosion. In fact, these predators don't even appear in the argument until the Conclusion.

  2. Bad Conclusion Match Not Sampling1% picked this

    A highly general proposal is based only on an unrepresentative set

    This answer refers to one of the 10 famous flaws, Sampling, in which the argument relies on a sample that may be too small, biased, or unrepresentative. This argument doesn't rely on any move from a specific sampling of facts to a general proposal. Both the evidence and the conclusion are focused on the same issue, same scope, same facts. It's hard to call this conclusion a "highly general" conclusion. It's specifically calling for predators to be brought in to eradicate rodents in order to prevent erosion of certain embankments. And even if the facts we learned, about these embankments and their rodent problems, are not typical, it doesn't matter. The argument isn't claiming they are typical. It's just recommending a solution to this situation, whether it happens to be a typical or atypical situation.

  3. Not Circular1% picked this

    The conclusion is no more than a restatement of one of the pieces of evidence

    This answer refers to one of the 10 famous flaws, Circular Reasoning, in which the author's premise restates the conclusion or requires the conclusion to be true. These answers are almost always wrong. The conclusion clearly is not restating anything in the premise, given that the notion of "predators" only appears in the conclusion.

  4. Bad Conclusion Match5% picked this

    One possible solution to a problem is claimed to be the only possible solution

    This answer sounds a bit like the #1 famous flaws, Necessary vs. Sufficient, in which the argument presents a conditional logic premise but then illegally applies that rule in a backwards or negated fashion. Saying that "X would fix it, but X isn't required to fix it" is synonymous with saying "X is sufficient but not necessary". However, the easiest way to see this answer is wrong is just to check whether the author concludes that bringing in predators is the only solution to the problem. She does not. The conclusion just promises that it is a solution, not that it's a required solution. The latter would have sounded like, "Therefore, we will have to bring in predators to prevent erosion."

  5. Correct89% picked this

    An action that would eliminate one cause of a problem is treated as if it would

    Why this is right

    The problem we were trying to solve is the erosion of the embankments. We currently have grass and woody plants attempting to solve that problem. The roots of the plants are suppose to provide firm support to keep the embankment from crumbling due to erosion. However, roots are struggling: 1. when we mow, grass clippings suffocate the plants, which causes their roots to rot. 2. the grass clippings also attract rodents, whose burrowing activities damage the roots. The author presents a solution of "bring in predators to eradicate the rodents". While that will help with problem #2, it will do nothing to help with problem #1. Thus, it's true to say the author treats "bringing in predators", which only solves part of the problem, as though it will solve the entire problem of damaged roots / erosion prevention. (Maybe a better solution would be to rake up the grass clippings so that the plants can breathe and so that rodents aren't attracted to the area.)

    Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.

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