## Sufficient v. Necessary assumption questions

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dowu

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Joined: Wed Mar 28, 2012 9:47 pm

### Sufficient v. Necessary assumption questions

So, I've been using the negation technique for necessary assumptions and its been working decently well.

However, I was reading through the Super Prep book and missed a sufficient assumption question. I read the explanation in the back and the writers stated that if the assumption (the correct answer choice) were false, then it would hurt the arguments conclusion. Therefore, this is why it is correct.

My question for you, then, is: Does the negation technique work for both kinds of assumptions? It seemed to work on this one, but I havent tried it on others. I'm just wondering if I should be negating the answer choices in all assumption questions.

Thanks!

dkb17xzx

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Joined: Wed Jan 20, 2010 6:25 pm

### Re: Sufficient v. Necessary assumption questions

Bump. I am interested in this as well.

kaiser

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Joined: Mon May 09, 2011 11:34 pm

### Re: Sufficient v. Necessary assumption questions

Negation technique can't work for sufficient assumption questions. Just think about it. A necessary assumption is absolutely necessary for the argument to work. Without it (i.e. if you negate it), then the argument falls apart entirely. Thus, by negating the correct answer, you know you have the right one since the argument is destroyed without it.

In a sufficient assumption question, you are looking for one of possibly infinite choices that would allow the conclusion to follow deductively. If you negated that sufficient assumption, there could be a million others that would satisfy what we are looking for. Thus, negation is improper for a sufficient assumption question.

suspicious android

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Joined: Tue Feb 09, 2010 4:54 pm

### Re: Sufficient v. Necessary assumption questions

The negation technique sometimes shows the correct response on a sufficient assumption question. Logically speaking, it doesn't have to. It often doesn't. It sometimes works because sufficient assumptions may be necessary as well (kind of like a biconditional). In that case, the negation technique would work, but basically by accident. Somewhat more commonly, a sufficient assumption will so straightforwardly complete the line of reasoning that its absence would make the argument seem awkward and jumpy. That's not the reason why it would be the correct response, but it can kind of point out why the idea is in fact important to the argument.

I don't think this is a good way to approach sufficient assumption questions, but I have to admit, it does end up working a fair bit of the time, in a "close enough for government work" kind of way. Of course, there are traps set on harder questions to make this not just unworkable, but completely counterproductive.

I actually don't really like the negation technique itself that much. While when used properly it works 100% of the time ("If do right, no can defend." -- Mr. Miyagi), it kind of masks the idea behind the question, and encourages people to think solely in mechanical terms instead of trying to understand the argument and its flaws. But it is a nice thing to be able to do.

dowu

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Joined: Wed Mar 28, 2012 9:47 pm

### Re: Sufficient v. Necessary assumption questions

suspicious android wrote:The negation technique sometimes shows the correct response on a sufficient assumption question. Logically speaking, it doesn't have to. It often doesn't. It sometimes works because sufficient assumptions may be necessary as well (kind of like a biconditional). In that case, the negation technique would work, but basically by accident. Somewhat more commonly, a sufficient assumption will so straightforwardly complete the line of reasoning that its absence would make the argument seem awkward and jumpy. That's not the reason why it would be the correct response, but it can kind of point out why the idea is in fact important to the argument.

I don't think this is a good way to approach sufficient assumption questions, but I have to admit, it does end up working a fair bit of the time, in a "close enough for government work" kind of way. Of course, there are traps set on harder questions to make this not just unworkable, but completely counterproductive.

I actually don't really like the negation technique itself that much. While when used properly it works 100% of the time ("If do right, no can defend." -- Mr. Miyagi), it kind of masks the idea behind the question, and encourages people to think solely in mechanical terms instead of trying to understand the argument and its flaws. But it is a nice thing to be able to do.

Yeah, I completely agree with this. I do, however, find that if I understand whats going on in the argument and can find whats missing (i.e., the gap in the argument) or even just a word or two of the gap, then I can look for those words and negate the answer choices accordingly. That way, I will have narrowed down the answer choice to the ones that seemed to fill the gap and narrow it down one last time using the negation technique.

LSAT Blog

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### Re: Sufficient v. Necessary assumption questions

+1 to both kaiser and suspicious android.

The OP's question is addressed further here:

viewtopic.php?f=6&t=171115