To strengthen an argument, you must first know its weaknesses


If your car was sputtering around like some cartoon jalopy from the 1920s and you wanted to fix it, you’d have to pop the hood to figure out what was going wrong with the engine (OK, I actually don’t know anything about cars, but I’ve been to enough repair shops where guys with oil on their hands and names on their shirts drone on about crank shafts and drive belts to know that this is how it works). Also, if you, say, wanted to know why your laptop is running slow, you’d want to go to like, the kind of weird programs on your laptop called “Activity Monitor” and look at graphs of your CPU and memory and figure out what’s slowing it down (I mean, I don’t know anything about computers either, but I did catch the movie Hackers on cable at some point and feel like I got the gist of it). And if you want to build a strong, more loving and lasting relationship with your SO, you’d want to figure out whether there are any underlying issues between you two, and work on those (again, so I’m told).

The point is, when we have to fix something in real life, we know we first have to identify the problem. We know this is true even in areas in which we have little knowledge or expertise. It would be nice if there was a button you could hit that would make your car run great, or a key we could strike that would solve all our computer issues, or some magic potion that would solve any relationship problem, but we understand this isn’t the case. And yet, when people are asked to fix stuff on the LSAT, this understanding flies out the window.

On the LSAT, there’s a whole family of Logical Reasoning questions that ask you to fix stuff. We call these questions Operation questions. Some might ask you to strengthen an argument, some might ask you to identify different kinds of assumptions that would strengthen the argument in a specific way, and some ask you to resolve discrepancies or explain unexpected phenomena. And you’ll get a ton of these questions. On the typical LSAT, about half of the LR questions will come from this family.

The most common question in this family–and the most common question on recent LSATs–ask you to strengthen an argument. There may be between 8 and 10 of these questions on a given LSAT, meaning up to 20% of Logical Reasoning will involve strengthening arguments. (This is one way, incidentally, that the LSAT does prepare people for law school and a legal career. Once you’re a lawyer, you’ll be sitting in an office with a framed J.D. and an oak-paneled desk and will have clients come in with trash arguments about, say, why they are owed money or shouldn’t have to give up a ton of money or, like, don’t deserve to go to jail. It’ll be your job to take their garbage arguments and improve them, so that they are presentable to a judge, jury, or settlement table).

When first encountering these questions on the LSAT, students think they can skip straight to the “fixing” part, without having to identify the problem with the argument. They see the conclusion, realize they have to make that conclusion stronger, and start looking for the answer choice that appears to do that. The problem with this technique is that, with the exception of a few easy questions, the way the right answer fixes the argument is almost never readily apparent. This is because the right answer will almost never say something as head-smackingly obvious as “Yes, good test taker, this conclusion is almost certainly true!” Instead, it’ll say something to the effect of “Ahh, clever test taker, that potential problem you identified with this argument isn’t actually a problem in this case” (I’m paraphrasing). Worse still, there will usually be a few incorrect answer choices that appear to directly support the conclusion, but actually have no effect on that conclusion.

Take this question from the June 2005 exam in which we’re asked to strengthen the argument. The question tells us:

“Over the last 10 years, there has been a dramatic increase in the number of people over the age of 65 living in this region. This is evident from the fact that during this time the average age of people living in this region has increased from approximately 52 to 57 years.”

So we’re trying to prove that there’s been a dramatic increase in the old folks moving into this area. There are a ton of things we could predict that, by themselves, would make this conclusion more likely to be true. There was a compelling ad for this region in AARP the Magazine. This region has a cable station dedicated solely to Fox News and Matlock marathons. The region’s hottest restaurant is an old-timey diner where elderly couples eat completely silent dinners at 4 pm. This region is Boca Raton, Florida and it is 1994. And so on.

However, the right answer will instead fix the fallacious reasoning this author uses when leaping from the evidence that “the average age has increased from approximately 52 to 57” over the last ten years to the conclusion that this means a lot of people over 65 have been moving in. And, in this case, the problem with this argument is that the author is ignoring the other ways the average age of a population could go up. Like a bunch of young people moving out (or I guess like an increase in the infant mortality rate or mass sterility or something–but the LSAT, despite occasionally being a total bummer, is rarely this dystopic).

So the clever, prepared test taker is looking for an answer choice that rules out one of these other ways the average age of a region could go up. That would fix this problem. The unprepared test taker is looking for something that will just kind of say more old people are moving in. The clever, prepared test taker would see (A)–which says “The number of people in the region under the age of 18 has increased over the last 10 years”–and immediately know that it rules out the possibility that a young people are moving out, which in turn strengthens the idea that the increased average age is due to old people moving in. She would select that and move on to the next question, earning her point and saving valuable time.

The unprepared test taker would see that, and be like “18 year olds? Why do I care about those entitled mouth breathers? Plus this is saying that a different group of people are moving in, so this might even weaken the argument.” And he would move on to something like (D)–which says “The number of people who moved into the region over the last 10 years is greater than the number of those who moved out.” And he would probably think, “I mean this doesn’t exactly say that people over 65 are moving in, but it does say that a lot of people are moving in, and that probably includes some old people, so this seems close enough.” And he would get that wrong because, even if (D) is true, it’s entirely possible that this average increased by having a ton of 58 year olds move in, replacing some babies who are moving out.

This question is illustrative. Many of the right answers to these strengthen questions will fix the problem you identify in the argument, like (A) did for the above questions. And many incorrect answers will, at first blush, appear to directly strengthen the conclusion, but actually have no effect on the conclusion, like (D). So you need to be prepared and always identify the problem with the argument first.

How can you do that consistently? Well, you can start by having a strong grasp of the logical fallacies that are commonly committed on the LSAT. The above question commits what we call the “exclusivity fallacy,” since the author is assuming that the increasing average age in the reason can be explained exclusively by an increase in the number of AARP members moving in, ignoring all the other ways the average age could go up. If you practice identifying these fallacies consistently, you’ll have seen that super common exclusivity fallacy many times over, and will be well prepared to identify it in this case.

Additionally, knowing which fallacies appear all the time on the various types of Operation questions can give you a head start on identifying the problem. Almost half of all strengthen questions, for instance, commit a causation fallacy. Again, the problem in the above question could be framed this way, since the author is assuming that an increase in 65 year olds is causing the average age to go up. And one way to strengthen a causal argument is to rule out alternate causes, as (A) does. So checking to see if that problem is present will allow you to find the problem quickly on many questions.

No matter what, for these strengthen questions, you need have an idea about what the problem is in the argument before looking at the answer choices, so you know which answer choice will actually improve the argument by fixing that problem. Don’t expect the answer choices to both reveal the problem and fix the problem for you. Like the auto mechanic, a slow laptop, and an angry significant other, they are not your friends.

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