## Necessary Assumption Approach Discrepancy

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mcs268

Posts: 249
Joined: Fri Dec 24, 2010 1:03 pm

### Necessary Assumption Approach Discrepancy

So, I know that it is generally taught that in necessary assumption questions, the right answer must account for a new element in the conclusion. However, I'm very confused because I've run into a problem where this does not happen. It is on Prep test 36 December 2001 Section 3 #14.

The new element in the conclusion is clearly "a more traditional education stressing verbal and quantitative" skills but the correct answer does not have that info. I see how the correct answer (C) makes since, but I eliminated it on first glance.

I understand you have to be flexible with the "approaches", but this scares me because what if this happens on the real test and I eliminate the correct answer by mistake?? Is there some way I can tell when the new element DOESN'T need to be in the answer?

I'm thinking in this case "most" is important, so is it certain qualifiers like that which should preclude any eliminations for the "new element"

Thanks! (and I'm sure this will be helpful to most)

dowu

Posts: 8300
Joined: Wed Mar 28, 2012 9:47 pm

### Re: Necessary Assumption Approach Discrepancy

mcs268 wrote:So, I know that it is generally taught that in necessary assumption questions, the right answer must account for a new element in the conclusion. However, I'm very confused because I've run into a problem where this does not happen. It is on Prep test 36 December 2001 Section 3 #14.

The new element in the conclusion is clearly "a more traditional education stressing verbal and quantitative" skills but the correct answer does not have that info. I see how the correct answer (C) makes since, but I eliminated it on first glance.

I understand you have to be flexible with the "approaches", but this scares me because what if this happens on the real test and I eliminate the correct answer by mistake?? Is there some way I can tell when the new element DOESN'T need to be in the answer?

I'm thinking in this case "most" is important, so is it certain qualifiers like that which should preclude any eliminations for the "new element"

Thanks! (and I'm sure this will be helpful to most)

I'm sorry, but if I understood what I read correctly in a few of my LSAT prep books, in a Sufficient Assumption question, you will be looking to bridge the gap, or as you say, account for a new element in the conclusion. Again, thats for sufficient assumption questions.

A necessary assumption question will not do this, and the harder necessary assumption questions' answers will look like they're out of scope, so you need to be careful with eliminating the correct answer choice.

Have you utilized the necessary assumption negation technique?

mcs268

Posts: 249
Joined: Fri Dec 24, 2010 1:03 pm

### Re: Necessary Assumption Approach Discrepancy

I'm getting mixed messages about the Necessary Assumptions. I use Manhattan LSAT forums for explanations usually and for this question they didn't mention this gap/new element thing, but in their other explanations they always say "necessary assumption...look for the gap!"

I use the negation test when I'm down to two choices or so, and I usually get it right. Sometimes though with the negation I'll still get it wrong because I'm still not clear on what's relevant to the actual argument (the test depends on you knowing the argument 100%, essentially).

Ugh these questions are just gonna be the death of me. 75% of my mistakes are on these, and I'm barely improving.

dowu

Posts: 8300
Joined: Wed Mar 28, 2012 9:47 pm

### Re: Necessary Assumption Approach Discrepancy

mcs268 wrote:I'm getting mixed messages about the Necessary Assumptions. I use Manhattan LSAT forums for explanations usually and for this question they didn't mention this gap/new element thing, but in their other explanations they always say "necessary assumption...look for the gap!"

I use the negation test when I'm down to two choices or so, and I usually get it right. Sometimes though with the negation I'll still get it wrong because I'm still not clear on what's relevant to the actual argument (the test depends on you knowing the argument 100%, essentially).

Ugh these questions are just gonna be the death of me. 75% of my mistakes are on these, and I'm barely improving.

Well, yeah, in both types of assumption questions, you're essentially looking for a gap. The difference is is that in sufficient assumption questions, the conclusion will normally have some new element that you must look for in the answer choices. If not in the conclusion, you'll see premises that are disconnected because of information that is in one premise but is not in the other. The premise gap happens less often than a new element being introduced in the conclusion.

For sufficient assumption questions, its easier to take a mechanistic approach and try to find the "gap" by simply looking for the new element. Once you've found the new element, you can usually eliminate the answer choices down to two, leaving two that contain said element. Then, its a matter of seeing which one actually bridges the argument by placing it into the argument and seeing how it flows. A common mistake by test takers is to not refer back to the stimulus' conclusion/premises when you think you've found an answer choice. You should be doing this more often if you're not.

As for the necessary assumptions, you need to find the answer choice that if it was negated, it would destroy the argument. If you negate an answer choice and then say to yourself, "yeah, so what. How does that affect the argument?", then you've probably found another incorrect answer choice. You need to be able to say, "shit, the conclusion cannot possibly follow from this statement".

Hope that helps!

kaiser

Posts: 2878
Joined: Mon May 09, 2011 11:34 pm

### Re: Necessary Assumption Approach Discrepancy

Be very clear what you are looking for in each type of question.

A necessary assumption is something that absolutely must be there or else the argument falls apart. It functions like a life vest in that it serves to keep the argument just above water, and without it, the argument drowns. Thus, the necessary assumption is something that you need to make it possible for the conclusion to make sense. The necessary assumption is not part of the conclusion. Rather, it is an unstated premise that must be within the argument, or else the conclusion cannot logically follow. A necessary assumption does not guarantee that the given conclusion will follow, but it makes it possible.

A sufficient assumption is one that guarantees the truth of the conclusion. Dont think of it as a mere life vest because it is much more. It makes it not just possible for the conclusion to follow (like a necessary assumption), but makes it so the conclusion given absolutely has to follow. A sufficient assumption makes it so the conclusion deductively follows from the premises, whereas a necessar assumption merely makes it possible for the conclusion to follow.

This is how you conceptualize assumption questions, so be very clear with what you are looking for since I think you are over complicating and over thinking it.

mcs268

Posts: 249
Joined: Fri Dec 24, 2010 1:03 pm

### Re: Necessary Assumption Approach Discrepancy

As I tend to overthink everything in this test as in life haha. Thank you both, hopefully I can improve before Oct 6.

dowu

Posts: 8300
Joined: Wed Mar 28, 2012 9:47 pm

### Re: Necessary Assumption Approach Discrepancy

mcs268 wrote:As I tend to overthink everything in this test as in life haha. Thank you both, hopefully I can improve before Oct 6.

You can and you will - keep chuggin my friend! Happy studying!

03152016

Posts: 9187
Joined: Wed Dec 21, 2011 3:14 am

### Re: Necessary Assumption Approach Discrepancy

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Last edited by 03152016 on Tue Mar 15, 2016 3:08 am, edited 1 time in total.

dowu

Posts: 8300
Joined: Wed Mar 28, 2012 9:47 pm

### Re: Necessary Assumption Approach Discrepancy

Max324 wrote:Reposting this from our October thread:

Max324 wrote:
Oscar85 wrote:Also, assumptions are a big part of the LSAT. I am good at identifying them once I read the answer choices, but I would like to improve my intuition abilities. What did you guys do to spot assumptions + come up with a good answer before reading the answer choices?

Sometimes you can pre-phrase, sometimes you can't. You can often pre-phrase supporter or sufficient assumption questions by "jumping the gap", that is, figuring out where the gap in logic is, and how to bridge the gap.

For example, if I see a premise in a sufficient assumption question that says "Only cool people listen to jazz", and my conclusion is "Therefore, Max is cool", I might pre-phrase, "Max listens to jazz". Why? I know that Max -> Cool, and I know that Jazz -> Cool, so if I assume that Max -> Jazz, the conclusion follows (in other words, Max -> Jazz -> Cool). Note that in this example, it is sufficient, but not necessary for Max to be cool; this would be an inappropriate pre-phrase for a necessary assumption question.

You (usually) can't pre-phrase defender assumption questions.

Posted this a couple times before; once more couldn't hurt:

A correct sufficient assumption answer triggers the conclusion, regardless of whether it links the premises (however, it's exceedingly rare that it won't link). Sufficient assumption answers are not necessary to the conclusion.

Example 1:
I ate bacon. Therefore I became fat.
Sufficient assumption: The high calorie count of bacon causes people who eat it to become fat.
Does it link? Yes. It links the consumption of bacon with becoming fat.
Necessary to the conclusion? No. Suppose that the high calorie count of bacon does not cause people who eat it to become fat. I can still justify the conclusion if, say, bacon contains enzymes that slows down metabolism, resulting in weight gain.

Example 2:
All carnivores eat bacon. Therefore, Jason eats bacon.
Sufficient assumption: All people who are not named Mark eat bacon.
Does it link? No. The carnivore aspect of the argument remains unaddressed.
Necessary to the conclusion? No. Perhaps some people who are not named Mark do not eat bacon. That doesn't necessarily prevent Jason from eating bacon.

A correct necessary supporter assumption links the premises, and is necessary to the conclusion.

Example:
I became fat. Therefore, I must have eaten bacon.
Necessary supporter assumption: Only if one has eaten bacon can one become fat.
Necessary to the conclusion? Yes. Suppose that one can become fat even if they have not eaten bacon. I can no longer justify my conclusion that I must have eaten bacon.

A correct necessary defender assumption defends against a weakener, and is necessary to the conclusion.

Example:
I became fat. The cause of this must have been the bacon I ate.
Necessary defender assumption: Bacon does not contain negative calories that cause people who eat it to lose weight.
Necessary to the conclusion? Yes. If bacon does cause people to lose weight, my conclusion is undermined.

This post is such a slut.

Oscar85

Posts: 71
Joined: Wed Jun 20, 2012 2:53 pm

### Re: Necessary Assumption Approach Discrepancy

Max324 wrote:Reposting this from our October thread:

Max324 wrote:
Oscar85 wrote:Also, assumptions are a big part of the LSAT. I am good at identifying them once I read the answer choices, but I would like to improve my intuition abilities. What did you guys do to spot assumptions + come up with a good answer before reading the answer choices?

Sometimes you can pre-phrase, sometimes you can't. You can often pre-phrase supporter or sufficient assumption questions by "jumping the gap", that is, figuring out where the gap in logic is, and how to bridge the gap.

For example, if I see a premise in a sufficient assumption question that says "Only cool people listen to jazz", and my conclusion is "Therefore, Max is cool", I might pre-phrase, "Max listens to jazz". Why? I know that Max -> Cool, and I know that Jazz -> Cool, so if I assume that Max -> Jazz, the conclusion follows (in other words, Max -> Jazz -> Cool). Note that in this example, it is sufficient, but not necessary for Max to be cool; this would be an inappropriate pre-phrase for a necessary assumption question.

You (usually) can't pre-phrase defender assumption questions.

Posted this a couple times before; once more couldn't hurt:

A correct sufficient assumption answer triggers the conclusion, regardless of whether it links the premises (however, it's exceedingly rare that it won't link). Sufficient assumption answers are not necessary to the conclusion.

Example 1:
I ate bacon. Therefore I became fat.
Sufficient assumption: The high calorie count of bacon causes people who eat it to become fat.
Does it link? Yes. It links the consumption of bacon with becoming fat.
Necessary to the conclusion? No. Suppose that the high calorie count of bacon does not cause people who eat it to become fat. I can still justify the conclusion if, say, bacon contains enzymes that slows down metabolism, resulting in weight gain.

Example 2:
All carnivores eat bacon. Therefore, Jason eats bacon.
Sufficient assumption: All people who are not named Mark eat bacon.
Does it link? No. The carnivore aspect of the argument remains unaddressed.
Necessary to the conclusion? No. Perhaps some people who are not named Mark do not eat bacon. That doesn't necessarily prevent Jason from eating bacon.

A correct necessary supporter assumption links the premises, and is necessary to the conclusion.

Example:
I became fat. Therefore, I must have eaten bacon.
Necessary supporter assumption: Only if one has eaten bacon can one become fat.
Necessary to the conclusion? Yes. Suppose that one can become fat even if they have not eaten bacon. I can no longer justify my conclusion that I must have eaten bacon.

A correct necessary defender assumption defends against a weakener, and is necessary to the conclusion.

Example:
I became fat. The cause of this must have been the bacon I ate.
Necessary defender assumption: Bacon does not contain negative calories that cause people who eat it to lose weight.
Necessary to the conclusion? Yes. If bacon does cause people to lose weight, my conclusion is undermined.

Yes I was quoted!! But yeah, listen to what Max has to say. He gives a very good description of assumption questions. Also, you will get them. I have been doing them for the past couple of days, and I have been getting better at them when I don't rush. Manhattan LSAT just confuses me at times because I sometimes can't determine what to include in my "core" argument...

Dookie39

Posts: 21
Joined: Sun Apr 29, 2012 11:15 pm

### Re: Necessary Assumption Approach Discrepancy

My understanding of the differences is that a necessary assumption question is something that is unstated, but that is required given the validity of the conclusion. It doesn't make the conclusion true, but if the conclusion is true, then this unstated premise must also be true. In essence, the conclusion is sufficient for the assumption to happen, almost like a must be true question is some ways, except those can be almost anything that has to be true related to the argument, whereas as an assumption question strictly asks for an unstated premise (which often backs up an unsubstantiated claim) that must be true given the conclusion. On the other hand, a sufficient assumption question is like a very strong strengthen question, in that if the assumption is true, then the conclusion must follow. The LRB calls these Justify the Conclusion questions which I think is much easier to think about when answering the question. You're essentially "proving" the conclusion with these, and the arguments are often pretty obviously flawed. I know this is kinda hard to read, but once you do a bunch of these, the differences become really clear.