#9 - To use the pool at City Gym, one must have a membership

[Administrator]

Complete Question Explanation

Flaw in the Reasoning—SN. The correct answer choice is (B)

The argument in this stimulus has a very straightforward structure. It begins by stating a conditional rule: “to use the pool at City Gym, one must have a membership there.” Though people often forget its classification, “in order to” is a sufficient condition indicator. Here, that phrase is shortened as “to.” We can diagram the statement as:

CGP = use the pool at City Gym
M = membership there

• Sufficient Necessary
  
  CGP M

Next, we are told that Sarah has a membership at City Gym. This means that Sarah has satisfied the necessary condition above. This tells us nothing definitive, because Sarah has satisfied the necessary condition, not the sufficient condition. To think we can infer something from this information would be a Mistaken Reversal. However, a Mistaken Reversal is precisely what occurs next, as the argument concludes that Sarah must use the pool at City Gym at least occasionally. Do not let the phrase “at least occasionally” throw you off. It plays no significant role in this sentence, and is simply meant to cloud the conditionality, which we can diagram as:

• MSARAH CGPSARAH

The question stem tells us this is a Method of Reasoning—Flaw question. Our preprhase is that the argument uses flawed conditional reasoning, reaching its conclusion by means of a Mistaken Reversal.

Answer choice (A): This answer choice can be confusing for those who realize that a Mistaken Reversal is mistaken precisely because it treats something that could be true as if it must be true. To clarify, when we are told that Sarah has a membership at the gym, all we can say is that she might use the pool. To say that she must use the pool is a Mistaken Reversal. This answer choice appears to be playing on that idea of possibility (“exceptions are made”) versus certainty (“strictly enforced”).

Answer choice (B): This is the correct answer choice, because it describes a Mistaken Reversal. Always remember, in a Method of Reasoning—Flaw question, if you know that an error of conditional reasoning occurred in the stimulus, look for answers that use the words “sufficient” or “necessary,” or words synonymous in meaning to them. In this case, the word “ensures” and the word “required” are used.

Answer choice (C): This describes a False Dilemma, in which the author assumes that only two courses of action are available when there may be others.

Answer choice (D): This describes an Error of Division, in which the author attributes a characteristic of the whole to a part of the group.

Answer choice (E): This describes a Circular argument, in which the author assumes as true what is supposed to be proved.

[Khodi7531]

Hey so I just did a 1-11 and got only this one wrong. I knew exactly it was a mistaken reversal...but when I broke B down, I didn't understand it to mean nec for suff swap.


so P > M
M
------
So, P.



I read the a/c as "treats whos truth is required for the conclusion" as P. But when these answer choices that bring up confusing language like this, am I supposed to be looking at the conclusion of the argument?

Like M > P - I should be attacking THIS right? with B it would mean it's false because the conclusion is assuming the conclusion is P and having M ensures P.

[Adam Tyson]

Sounds like you are on the right path, Khodi. First, you correctly identified the flaw as a Mistaken Reversal when you read the stimulus. That gets you halfway home! Now all you have to do is find an answer choice that describes that kind of flaw.

The authors of this test are really, really good at confusing us with complex wording. We cannot count on the answer being clear and easily understandable, using common speech patterns. Nope, we should instead expect a lot of lawyer-talk. Still, they have to talk about the right kinds of concepts, no matter how they do it, and when the flaw is conditional, that means they will almost certainly use terms found in conditional reasoning. They are probably going to talk about "conditions" and "sufficient" (or a synonym like "enough") and "necessary" (or synonyms like required, guaranteed, proven, must, certain, etc.) Answer B has all the right ingredients, using that mechanical approach - it uses "ensures" (another synonym for "sufficient"), and also "required" (necessary).

In this case, none of the other answers use any of the language of conditionality, so that should be enough for us to pick B even absent a clear understanding of what the heck they said! However, we would like to do better than that when we can, so let's dig into this one a little deeper.

"Required for the conclusion to be true": Well, the conclusion is that she uses the pool, so we are looking for something that is required for anyone who uses the pool. What is required for using the pool? A membership. So, "she has a membership" is the statement that is required in order for her to use the pool. Does she use that same statement (she has a membership) as ensuring that the conclusion is true (she uses the pool)? Yup, that's what she did! By applying the details of the stimulus to the abstract terms of the answer choice, we can make better sense of what we are reading. What is this statement they referred to? What is the conclusion that they say is true? Bring those details back in, and it all becomes clearer. Their fancy talk answer turns out to translate to a plain English restatement of the (bad) argument.

Understanding is great, and I don't want to discourage you from striving for understanding, but you should also remember that ultimately you do not always have to completely understand what you are reading, either in the stimulus or in the answer choices. As long as you can identify the underlying type of reasoning and the structure of the argument, you should be able to confidently eliminate wrong answers and get down to one or two contenders. If four answers are clearly wrong, and one answer is something you don't entirely understand, that's the best answer! "I don't get it" is much better than "that's wrong", right? Don't hesitate to pick an answer just because you don't understand it. Just call it a contender, move on to the other answer choices, eliminate the losers, and if only only one contender remains, pick it with confidence and move on to the next question.

I hope that helps!

[lsatstudying11]

Hi,

I had a question about answer choice D. What if it had said something like, "Concludes that Sarah does something (uses the pool) because all people who do that thing share an attribute with Sarah (have a membership)."

I know that this sounds convoluted and not LSAT-y, but I was wondering if something like this could accurately describe the flaw? Thanks

[Adam Tyson]

That would work, lsatstudying11! And given how slippery LSAC has gotten in recent years, and how they have been trying to find new and creative ways to craft answers that would not be as obvious to prepared test takers as answer B is in this case, I would not be at all surprised to see an answer choice very much like the one you created on a more modern test. They could give us a classic conditional flaw and then provide an answer that uses no conditional indicators and still be correct! Don't look now, but you're thinking like an LSAT author!

[cd1010]

Hello -- Just to clarify, "ensures that the conclusion is true" means treating the statement as a sufficient assumption, right?

[Luke Haqq]

Hi cd1010!

Yes, "ensures that the conclusion is true" is equivalent to saying that something is "sufficient to guarantee the conclusion."