How To Get Evaluation Questions Right in LSAT Logical Reasoning

So, you’re getting into your LSAT prep in a serious way. Like, you’re thinking of taking things to the next level; you may be ready to move in with your LSAT prep (and we all know that’s the fast track to either a messy breakup, or you and LSAT prep makin’ babies and gettin’ married). So you’re at the place where you’re ready to talk about Evaluation Questions. 

Now, if you’re not sure you’re that serious yet about LSAT prep? STOP READING. YOU MAY NOT BE READY FOR THIS JELLY.

For everybody remaining, OK, let’s do this.

First: Evaluation Questions are pretty rare. Don’t expect to see more than one of these on the entire test. Still, they are nowadays asked on most tests, so you should be ready for them if you want that awesome high LSAT score. Don’t worry. This won’t hurt a bit.

The Evaluation Question is asked one of two main ways:

• Which of the following would be most helpful to know in evaluating the argument above?
• In order to evaluate the argument above, it would be most useful to know whether…

Remember the Proof Principle? No? OK, no worries. That principle simply tells us that a claim is proved if the evidence in favor of that claim is such that it is impossible for the claim to be false.

On the LSAT, we have stipulated the truth of any premise offered into evidence; thus, if we want to Evaluate an argument, then the only relevant question is whether sufficient evidence has been presented for the proof of the conclusion of that argument (now, how’s that for a rabbit-hole of prepositional phrases?).

Let’s do an example problem together. It will bring us closer. It will be nice. 

Here we go:

Kenya lives in a suburb of a large city, and works at a hospital in the city center. Since the bus line connecting the suburb where Kenya lives to the city center where she works has been temporarily taken out of service by the Metro Transit Authority, Kenya must now either buy a car or find a different job; after all, the distance between her home and the hospital is too great to allow her to walk to work each day for any more than about one week.

Let’s do a little identifyin’ now:

The Main Conclusion of the argument is that Kenya has to buy a car or find a new job.

The Premises (the pieces of evidence offered in the argument) are that she cannot walk to work every day for longer than about a week, and the bus line connecting her suburb to the city where her job is located is temporarily out of service.

Now, let us evaluate together: Does that evidence prove the conclusion? Nope. Course not. 

Here are four Necessary Assumptions of this argument (there are certainly more than four things missing from this argument, but we don’t have all day). What? Oh, you do have all day? Then you should spend some time compiling a list of other essential evidence needed to prove that Kenya has only two options left to her. Meanwhile, we’ll start with the following four assumptions:

1. The bus line will be out of service longer than a week.

2. Kenya does not now own a car.

3. Kenya cannot ride to work in a friend’s car.

4. Kenya works every day.

Since we’re dealing with Evaluation Questions, let’s translate the above into four pieces of information that would be useful to know in evaluating the argument:

1. How long will the bus line be out of service?

2. Does Kenya currently own a car?

3. Is there any way, other than walking, driving her own car, or riding the bus, that Kenya could get to work?

4. Does Kenya work each day?

Notice that each question above is an example of a correct answer choice to an Evaluation question. Notice also that each question above simply asks you whether or not some necessary assumption of the argument is true. Plus, check out what happens when you supply two opposing answers to those four questions:

1. How long will the bus line be out of service?

Answer A: More than a week. If that’s true, the argument becomes stronger; you’re saying that this necessary assumption is true.

Answer B: Less than a week. If that’s the case, this argument is ruined, because you are effectively negating a necessary assumption: Why buy a car or switch jobs when the argument allows that Kenya could walk to work for up to a week?

2. Does Kenya currently own a car?

Answer A: No. If that’s the case, you’ve affirmed the assumption and the argument is stronger for it.

Answer B: Yes. If she does own a car, you’ve negated a necessary assumption, and made the argument look foolish in the process.

3. Is there any way, other than walking, driving her own car, or riding the bus, that Kenya could get to work?

Answer A: No. If there’s no other way for her to get to work, then this argument is strengthened.

Answer B: Yes. If there is some other way to get to work, then once again, we’ve denied the truth of a necessary assumption and we’ve ruined the argument by doing so.

4. Does Kenya work each day?

Answer A: Yes. If she does, then the argument has a little more merit; we’ve asserted a necessary assumption.

Answer B: No. If she doesn’t work every day, then there’s no reason given by this argument against her walking to work. Here, we’ve killed the conclusion, which was based on the assumption that she has to work each day.

And there you have it; the only thing that could be useful to know in order to evaluate an argument is whether or not some necessary assumption is true.

Now use that knowledge to earn yourself some piping hot points on your next LSAT preptest.

Until next time, be logical, be brave, and be good to one another,

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