LSAT Question Explanation
PT 105, Section 1, Question 23
Necessary AssumptionArgument structure
Farmers who use deep tillage should instead use different aeration techniques and no-till methods.
Farmers who deep till are 10x more likely to lose topsoil to erosion than farmers who use no-till methods.
Explanation
This stimulus concludes that since deep-tilling is bad for the environment, we should use no-till methods. But the author hasn't proven that no-till is the only or best viable option besides deep-tilling. If there are other methods available, they could undermine our author's conclusion. Assumptions that would help the conclusion include eliminating viable alternatives.
Answer choices
We don't care about what farmers want to do, just what they actually do.
This shows a relative relationship between deeper deep-tilling and more extreme erosion. But the argument is just about the likelihood of experiencing erosion at all if one uses deep-tilling. We don't need to know that they scale at a relative rate.
We need this if we're going to conclude that the farmers should switch to no-till methods. If there's some alternative (medium-till?) then the conclusion may not be justified.
We don't need to know how much different methods cost, the author is just saying we should use no-till methods instead of deep-tilling because the author thinks deep-tilling is bad for the environment.
We don't need to know that no-till methods are more effective at aeration. The author was saying we should use them because he thinks they are better for the environment.