valid answer to necessary assumption question

wanderlust
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valid answer to necessary assumption question

Postby wanderlust » Sat May 05, 2012 1:16 pm

in questions like "which one of the following is an assumption on which the argument depends?"

Is that the case that the negation of the correct answer must hurt the conclusion directly.
I find sometimes the negation of the correct answer hurts the conclusion directly. sometimes it hurts the main evidence, instead of hurting the conclusion directly. With the main evidence toppled, the conclusion collapses,
Is there any pattern in the way that the correct answer choice in this type of question work? Anyone could help?
Thanks in advance!

kaiser
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Re: valid answer to necessary assumption question

Postby kaiser » Sat May 05, 2012 1:35 pm

The negation of the correct answer in a necessary assumption question makes it impossible for the conclusion to follow. The necessary assumption is like the life vest that is keeping the argument above water, and without it, the argument must by definition fall apart.

You are saying the same thing in various ways, but there is value in being concise and precise with your words: Negation of a necessary assumption doesn't "hurt the conclusion". Rather, it makes it so the conclussion cannot logically be reached from the premises.

wanderlust
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Re: valid answer to necessary assumption question

Postby wanderlust » Sat May 05, 2012 1:56 pm

kaiser wrote:The negation of the correct answer in a necessary assumption question makes it impossible for the conclusion to follow. The necessary assumption is like the life vest that is keeping the argument above water, and without it, the argument must by definition fall apart.

You are saying the same thing in various ways, but there is value in being concise and precise with your words: Negation of a necessary assumption doesn't "hurt the conclusion". Rather, it makes it so the conclussion cannot logically be reached from the premises.



Thanks a lot for the explanation!

In what way, do you think that the negation of a necessary assumption works?

Does it negate a premise? Or does it add a new premise, which when added to the original premises, let the conclusion fall apart.

For example, if the argument is "because of A, therefore B"
Does the negation of a necessary assumption work to say something along the line of "no, A does not exist, so we can't have B" or does the negation of a necessary assumption serve to say "A exists, but there is also C, so we can't conclude B"

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dowu
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Re: valid answer to necessary assumption question

Postby dowu » Sat May 05, 2012 2:38 pm

:shock: :shock:
Last edited by dowu on Sun Apr 17, 2016 7:34 pm, edited 5 times in total.

wanderlust
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Re: valid answer to necessary assumption question

Postby wanderlust » Sat May 05, 2012 2:53 pm

nmop_apisdn wrote:
wanderlust wrote:
kaiser wrote:The negation of the correct answer in a necessary assumption question makes it impossible for the conclusion to follow. The necessary assumption is like the life vest that is keeping the argument above water, and without it, the argument must by definition fall apart.

You are saying the same thing in various ways, but there is value in being concise and precise with your words: Negation of a necessary assumption doesn't "hurt the conclusion". Rather, it makes it so the conclussion cannot logically be reached from the premises.



Thanks a lot for the explanation!

In what way, do you think that the negation of a necessary assumption works?

Does it negate a premise? Or does it add a new premise, which when added to the original premises, let the conclusion fall apart.



The necessary assumption, in most cases, is the gap in the argument between a) the premises and the conclusion, and less often b) the gap between the premises.

In this way, you can see that once you have negated the correct answer choice, you will see that the conclusion does not follow and therefore this is your necessary assumption because without it, the argument would not work.

Also, you need to do the conditional reasoning drills in the LG bible, because it seems as if you don't really know about conditional reasoning.

wanderlust wrote:For example, if the argument is "because of A, therefore B"
Does the negation of a necessary assumption work to say something along the line of "no, A does not exist, so we can't have B" or does the negation of a necessary assumption serve to say "A exists, but there is also C, so we can't conclude B"


In the example you gave, you negated the antecedent (sufficient condition, A) to deny the consequent (the necessary condition, B) and this is invalid reasoning.

There are two main types of valid reasoning used on the LSAT known as Modus Ponens (MP) and Modus Tollendo (MT); look them up.

In short, MP is the affirmation of the antecedent, which leads to the affirmation of the consequent.
MT is the denial of the consequent to ensure the denial of the antecedent.

Here's a great article written by someone on TLS that you should check out and study pretty diligently until you know whats going on.

http://www.top-law-schools.com/conditio ... oning.html

You must print it out and do the work sheets that come with it.

Good luck!



Deep stuff!


Thank you so much!

You are right, conditionality, (and causation), is minefield to me. I'll definitely check out the resources you mention.

May I bother you with one more question?

Can I say that correct answer choice to a necessary assumption question could be

a) necessary assumption to make premise stand
b) necessary assumption to make intermediary conclusion stand
c) necessary assumption to make main conclusion stand

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dowu
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Re: valid answer to necessary assumption question

Postby dowu » Sat May 05, 2012 2:56 pm

:shock: :shock:
Last edited by dowu on Sun Apr 17, 2016 7:39 pm, edited 1 time in total.

wanderlust
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Re: valid answer to necessary assumption question

Postby wanderlust » Sat May 05, 2012 3:09 pm

nmop_apisdn wrote:
wanderlust wrote:Deep stuff!


Thank you so much!

You are right, conditionality, (and causation), is minefield to me. I'll definitely check out the resources you mention.

May I bother you with one more question?

Can I say that correct answer choice to a necessary assumption question could be

a) necessary assumption to make premise stand
b) necessary assumption to make intermediary conclusion stand
c) necessary assumption to make main conclusion stand


Yeah I believe so, amongst other things. But on the LSAT, you need to try and find the gap in the argument; what is the author missing?!

Oh, and my trick to negate answer choices quickly is just to start the sentence with "It is not the case that ______". This will lead to the negated version of the answer choice.

If you find that once you read the stimulus and the negated version makes the authors conclusion implausible, then you have found your answer!

Refer back to the lifejacket analogy above, as it gives a great illustration of how the necessary assumption works.


Thanks for sharing the trick of negation and the lifejacket analogy. I guess I often think that the premise is the lifejacket. If we get rid of the premise, we no longer have the conclusion. But as you said, it's actually a fallacy in conditional reasoning.

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dowu
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Re: valid answer to necessary assumption question

Postby dowu » Sat May 05, 2012 3:17 pm

:shock: :shock:
Last edited by dowu on Sun Apr 17, 2016 7:39 pm, edited 1 time in total.

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Nova
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Re: valid answer to necessary assumption question

Postby Nova » Sat May 05, 2012 3:33 pm

nmop_apisdn wrote:
Oh, and my trick to negate answer choices quickly is just to start the sentence with "It is not the case that ______". This will lead to the negated version of the answer choice.


Necessary assumptions are my favorite questions because of this.

Full proof.

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bdeebs
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Re: valid answer to necessary assumption question

Postby bdeebs » Sat May 05, 2012 4:03 pm

^^^nice pun.

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dowu
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Re: valid answer to necessary assumption question

Postby dowu » Sat May 05, 2012 4:06 pm

:shock: :shock:
Last edited by dowu on Sun Apr 17, 2016 7:39 pm, edited 1 time in total.

wanderlust
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Re: valid answer to necessary assumption question

Postby wanderlust » Sat May 05, 2012 4:43 pm

nmop_apisdn wrote:
Well yeah, merely getting rid of a premise isnt the correct way to find the correct answer for these questions. Again, you need to find the gap in the argument. These necessary assumption questions are sort of like strengthening questions in that you're looking for that unstated that that would bring the argument together. If all of the premises and the conclusion are true, then the necessary assumption will fill in any gaps in the argument.

Good luck!


Thanks a lot! Do you happen to have PT 33 at hand? Could you please take a look at S1 Q19? Do you think it is a rare case where the correct choice is a necessary assumption to the subsidiary conclusion, instead of the main conclusion?

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dowu
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Re: valid answer to necessary assumption question

Postby dowu » Sat May 05, 2012 4:56 pm

:shock:




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