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#12 - Though Earth’s human population is increasing

ynwasif
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A little trouble with this question, my pre phrase/idea of what I thought the answer would contain didn't seem apparent in any answer choice.

I ended up guessing this question but do not quite understand why B is correct. The only reasoning I could think of to see how B weakens the argument would be that if the amount of fresh water needed varies from region to region, it is not solely dependent on population growth trends, rather it can also be impacted by the access to fresh water.
Rachael Wilkenfeld
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Hi ynwasif,

Let's look at this stimulus. Our conclusion is that water shortages won't be a problem in the short term. Why? What's the support? Even though the Earth's population is increasing, we still are only using a small fraction of the supply of fresh water.

This is a weaken question, so your prephrase needs to help you think about what would attack that conclusion. A lot of people want a prephrase to state a specific answer choice they are looking for. But prephrasing often isn't that specific. I think of it as more of an art than a science. You may have a situation where you have a very precise prephrase. Stimuli with conditional reasoning often lead to very precise prephrases. But more frequently, like here, you'll have a more general prephrase. The trouble is, that oftentimes, students like specific prephrases, so it's tempting to turn a general prephrase situation into a precise prephrase situation.

Let's look at some examples of what this looks like in practice:

Imagine the following stimulus: If you are in law school, then you must have taken the LSAT. Kayla is in law school.
Question: Which one of the following must be true?

Our prephrase here can be VERY precise: Kayla has taken the LSATs.

Turning back to this stimulus in this question though, we have a different situation. Our stimulus doesn't yield anything nearly as specific. We have a conclusion that we don't need to worry about water running out because we currently only use a small fraction of available fresh water. We want to weaken this stimulus. We could come up with any number of specific prephrases. Maybe the even though there's fresh water, it's not useable for some reason. Maybe the fresh water is almost all underground. There are any number of possible things that would weaken the stimulus, so it's not particularly helpful to try to list them all. But we CAN come up with a general prephrase that would encompass all of the ideas. We are looking for an answer choice that gives us a reason that the fresh water available isn't sufficient to meet a growing population's needs. That's our prephrase.

Whew. With all that said, let's look at the answer choices.

Answer choice (A): Even if population trends are hard to predict, this doesn't explain why we couldn't use the fresh water that exists. If we are only using a "small fraction" of the available water, we could have fairly extreme population growth before it matters. This doesn't weaken, nor does it match our prephrase.

Answer choice (B): This is our correct answer. It shows that while there might be plenty of fresh water on Earth as a whole, it isn't distributed in a way that is sufficient for the population in every region. This means that an increasing population of Earch could easily cause a water problem, even if we aren't using all the available water.

Answer choice (C): This answer choice assumes that conservation would be needed. But if we aren't adopting conservation methods now, and still aren't using very much water, why would it be a problem if we didn't in the future? We need something to say that the amount of water is somehow insufficient for Earth's population's needs.

Answer choice (D): This looks like an interesting answer choice. But "eventually" outstripping resources is very different than the stimulus, which talks about water shortages in "the near future." The time shift here rules it out.

Answer choice (E): This one talks about how water is used by humans, but doesn't really give us a reason that we couldn't use more of the available fresh water. It doesn't match our prephrase or weaken the argument.

I know prephrasing is hard. It's a skill that takes a while to get the hang of, and the only way to improve is to keep trying and practicing. The more you do it, the easier it gets.

Hope that helps!
Rachael
ynwasif
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Hi Rachael,

Thanks for the detailed reply, I really appreciate it! Just to clarify, I was not looking for a specific pre phrase per se, I was more looking for something that would show that the current water supply wouldn't be enough.

I ended up choosing answer D, again it was a guess as it was the best answer I could see since I did not feel confident with the other answers. I understand from the explanation why D is wrong, but I am still struggling a bit to understand why B would be correct I was hoping you could maybe further clarify where my reasoning went wrong.

Here is the reasoning as to why I dismissed B as an answer on the test: If the amount of fresh water available to meet the needs of earths population varies significantly from region to region, I saw that as having no effect on the conclusion because:
1. it doesn't explicitly (though I can see implicitly) state that the regions with water that is not fresh are inhabited by many and
2. if there is not enough available fresh water in a region inhabited by many people, why could it not be used from other regions? In other words, why would B support that the current water supply is not sufficient, I see B as saying there is enough fresh water in the world, but some regions just don't have enough, why can't it be moved or used in other regions if the total fresh water supply is still there?
James Finch
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Hi ynwasif,

LR questions tend to be testing one or two specific concepts that the answer choices will bring up. With (D), we have an issue of careful reading and scope of claims: the stimulus is only concerned with the "near future," so something that will "eventually" happen may or may not occur within the "near future" window presented in the stimulus.

With (B), this question's author is testing how well you understand the relationship between whole groups and their constituent parts. If humanity as a whole will not be plagued by water shortages, then that means that no individual groups will be plagued by water shortages either, as the language creates a binary situation: water shortages? Yes/No.

Note that this isn't necessarily true of all group/member dynamics, as not all characteristics are binary in this way. For example, we could have a claim that Group X votes for party Y, but that would only mean that the majority of Group X votes for Party Y, not each individual member. The LSAT is pretty good about making this clear with qualifying language such as "likely," "probable," "usually," "most" etc. When the language used is an unqualified statement about a group, generally that means the statement would apply to all members of the group.

Back to the question, since we have an unqualified statement we can treat the characteristic as applying to the group as a whole as well as to individual members. In that case, if the situation of the group's members varies greatly, then it is much easier to have what is true of a group as a whole be false for some members of it. The stimulus is concerned with the near future and has already conceded that one characteristic of the group (population) is changing, but claims that because, in aggregate, only a small percentage of fresh water is being used, this must be true for the different parts of the group as well. But because we only have information about water supply in aggregate, and we are expected to know that some places on Earth are much drier than others, it is possible that some dry areas are already having water shortages (as a real life example, Cape Town, South Africa) even without factoring in a growing population, while other areas (Eastern Canada) don't have issues with water shortages and won't even if their populations grow.

I hope this clears things up!
ynwasif
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Joined: Tue Mar 19, 2019 1:32 pm
Points: 4

Hi James,

Thanks for the response, this definitely clears things up a bit more!