LSAT 59 - Section 2 - Question 10

We’ve got a Main Conclusion question which we know from the question stem: Which one of the following most accurately expresses the main conclusion of the argument?

Moving onto the stimulus:

We start out with the notion that chemical fertilizers are very bad for a couple reasons: 1) they create health issues and 2) they kill worms, which are beneficial for soil.

Then we get the word “for” which some of you may recognize as an indicator that precedes a premise but is often part of a sentence that also includes a conclusion. Interesting. Is that the case here? Let’s take a closer look.

We’re told “for this reason.” What reason? Well “this reason” is a referential phrase referring to the second effect of chemical fertilizers we were presented with in the opening sentence. If we insert the information that “this reason” is referring to and paraphrase a bit, the second sentence would read like: “Because fertilizers destroy earthworms, the use of chemical fertilizers should be avoided.” So now we can see that the opening clause of this sentence provides support for the second clause. We can apply the why test just to make sure: Why should we avoid chemical fertilizers? Well because fertilizers destroy earthworms. The only way we can work out the full meaning of this sentence though, is by unpacking the referential phrase within it. Ok so we’ve identified at least one premise and conclusion. Now let’s move on to the third sentence.

If we look closely at the third sentence we see the word “thus” which is a conclusion indicator. But I thought we already found our conclusion? Not so fast! We found one conclusion! That doesn’t mean there can’t be more! When we take a closer look, we find a conclusion in the second clause of this sentence immediately following the word thus: “a garden rich in earthworms is much more fertile than a garden without them.” Working backwards we can see support in the first clause of this sentence. Again, we can apply the why test to test this support relationship: Why is a garden rich in earthworms much more fertile than a garden without them? Well because the castings they leave behind are richer than the soil they ingest. That works! First clause premise, second clause conclusion.

Ok so now we’ve got two conclusions, but only one of these can be our main conclusion meaning one of them is a sub-conclusion that both lends and receives support. If we take a step back, we see that the second conclusion supports the idea that chemical fertilizers should be avoided, meaning that this first conclusion about chemical fertilizers is our main conclusion. Let’s return once more to our old friend Mr. Why Test: Why should the use of chemical fertilizers be avoided? Well because our first premise tells us that fertilizers kill earthworms and our sub-conclusion tells us that a garden rich in earthworms is much more fertile than a garden without them. Now that’s what I call support!

Ok so let’s revisit our main conclusion: “the use of chemical fertilizers should be avoided.” Let’s take a look at our potential answers:

Answer Choice (A) This correctly sums up our premise but is not part of our conclusion.

Answer Choice (B) Again, this refers, correctly to another aspect of our premise, but is not found in our conclusion.

Answer Choice (C) Another answer choice that accurately sums up one of our premises, but not our main conclusion.

Correct Answer Choice (D) This is verbatim the main conclusion we identified. Not much more we need to discuss there. Case closed. But since we’ve still got one more answer choice left, let’s go ahead and take a look.

Answer Choice (E) Ok yet another answer choice that correctly sums up part of our stimulus. In this case this is referring to our sub-conclusion. If you didn’t recognize that this is a sub-conclusion that actually supports our main conclusion, this might be a tempting AC.