December 2014 LSAT Section 4 Question 15

Economist: Many of my colleagues are arguing that interest rates should be further lowered in order to stimulate econ...

tomgbean on January 1, 2020

Why would answering this question require us to infer that there is indeed another reason to lower interest rates? the economists' colleagues are arguing for lowering interest rates in order to stimulate economic growth. The economists' argument is directly against this claim. So it is reasonable that the phrase "currently there is no need to lower interest rates" is in reference to lowering interest rates being sufficient for stimulating economic growth. So in other words, the economist is saying that there is no current need to lower interest rates in order to stimulate economic growth. Other reasons for lowering economic growth seems irrelevant in the context of the passage.

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SamA on January 15, 2020

Hello @tomgbean,

This is a strengthen w/necessary question, so remember that our conclusion depends entirely on this assumption. Simply strengthening the conclusion is not enough. We need to ask ourselves, "Does the argument need this to be true?"

Support: Diplodocus's bone structure would have prevented it from raising its neck.
Conclusion: Thus, Diplodocus must have fed on plants on or near the ground, or underwater.

First, we need to identify the answer choices that strengthen the argument. But then we need to decide which remaining answer choice is the necessary assumption. You were on the right track with A and C, as both strengthen the argument. However, you must proceed with the negation test. If we negate A or C, is the argument destroyed?

A. The same type of neck structure is NOT found on modern ground-feeding animals. Does this destroy the argument? No, Diplodocus could still have fed on plants on the ground. The argument does not need A to be true. Therefore it is not the necessary assumption.

C. It would be POSSIBLE for a large animal such as Diplodocus to supply blood to an elevated brain. Does this destroy the argument? No, because the limited mobility of the neck bones is still an issue. We don't care about the blood supply. Negating C does not affect the argument, therefore it is not the necessary assumption.

D. To negate, we will say that Diplodocus was able to reach high-growing vegetation by rising up on its hind legs. Does this destroy the argument? Absolutely. It makes the bone structure irrelevant. This is the only piece of support given by the argument. Without it, the conclusion falls apart. The author needs D to be true in order to draw the conclusion. This is the correct answer.

SamA on January 15, 2020

Hello @tomgbean,

Apologies, I copied the wrong answer. Please disregard my first response.

We do not need to be certain that there is another reason. However, we cannot say for certain that there isn't one. This is the error that the economist makes. The economist concludes that there is no reason, but he does not have enough information to make that conclusion. He has eliminated one reason for lowering interest rates, the one given by his colleagues, but does that mean there is no reason? No. Let's break down the argument.

Colleagues: Interest rates should be lowered in order to stimulate economic growth.
Premise: The economy is already growing at a sustainable rate.
Sub-Conclusion: No such stimulation is needed.

Up to this point, the argument seems valid. Maybe the economist has successfully countered his colleagues. However, he takes it too far with his main conclusion.

Conclusion: Currently there is no reason to lower interest rates.

What information does the economist have to support this? He only eliminated one possible reason. There may be plenty of other reasons to lower interest rates. Answer choice C most accurately describes this error in reasoning.