Logical ReasoningDifficulty: Hard

PT105 S1 Q23 Explanation

Deep tillage is even more

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

TopicsNecessary Assumption

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Stimulus

Deep tillage is even more deleterious to the world's topsoil supply than previously believed. For example, farmers who till deeply are ten times more likely to lose topsoil to erosion than are farmers who use no-­till methods. Results like these make it clear that farmers other topsoil aeration techniques, to incorporate no-­till methods instead.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

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

The question
23.

The argument depends on assuming which one of

Answer choices

  1. Out of Scope: want25% picked this

    Topsoil erosion does not make farmers want to till

    This answer is very tempting, and I would consider picking it if the correct answer weren't there. It has the lovable quality of ruling out an idea with the word "no/not". When we negate it, it starts to suggest Reverse Causality: topsoil erosion does make farmers want to till more deeply I'm surprised this answer choice is here, since it seems like we shouldn't be forced to compare (A) and (C) and ask, "Which is better?" However, if we need to, we can ask ourselves, "Which answer, if negated, most weakens", and the light suggestion of reverse causality we get from this answer isn't nearly compelling as the objection we get from (C). If LSAC had a different reason for thinking this answer was wrong, I would suspect it's either because 1. the issue isn't about whether it makes the farmers want to till more deeply but whether it requires that the farmers actually do till more deeply 2. the correlation might be tensed in a way that precludes Reverse Causality (f.e. "ppl who are X are more likely to develop Y" has a chronological dimension to it that sounds like they were X before they developed Y). If the correlation where phrased, "Farmers who till deeply are ten times more likely to have lost topsoil to erosion", then it's pretty ambiguous which came first. But because it says "to lose topsoil to erosion", it seems to imply a future condition that comes after the deep tilling has already started.

  2. Too Strong16% picked this

    In deep-tillage farming, the deeper one tills, the greater the susceptibility

    Too Strong: the more X, the more Y These kind of Volume Dial formulations are the most extreme type of statement we see on LSAT, because they extend infinitely in both directions. Does the author have to assume that 99 feet of deep tilling creates greater susceptibility to topsoil erosion than 98 feet of deep tilling? That 2cm of tilling creates more susceptibility than 1cm of tilling? The author definitely thinks that deep-tilling has a harmful effect on topsoil erosion, but it doesn't have to be an infinitely proportional connection as this answer describes.

  3. Correct45% picked this

    Tilling by any method other than deep tillage is not a

    Why this is right

    This also has the lovable quality of ruling out an idea using "no / not". If we negate it, do we get an Objection? Yes -- there is at least one tilling method other than deep tillage that is a viable option. This answer choice alerts us (if we didn't catch it previously) that the conclusion actually makes a False Choice. The author is shooting down deep-tilling, as it seems to be even worse than we thought. Thus, she concludes, farmers should switch to no-till methods. Are those the only two options? It's either deep-tilling or no tilling? What about light tilling? Medium tilling? If those are viable options too, then that greatly weakens her conclusion. (If you want to see a similar problem, check this out.)

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

  4. Trap1% picked this

    The most expensive farming methods employ topsoil aeration techniques other than

    Too Strong / Out of Scope: most expensive The passage never delves into the expense of different methods of tilling, so we have no reason to say the author has committed herself to believing anything about the most expensive farming methods.

  5. Too Strong: more aerated13% picked this

    On average, topsoil that is no-tilled is more aerated than topsoil that

    The author isn't endorsing no-till methods because she thinks they lead to more aerated topsoil. She's doing so because she thinks they lead to less topsoil erosion. We can't accuse her of believing that no-till is better at aerating than deep till. Even if they're just equally good at aerating the soil, the author's argument still works.

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