PT 29 sec 15- LR

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robotdreams
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PT 29 sec 15- LR

Postby robotdreams » Mon May 24, 2010 8:25 pm

As always help would be appreciated!

Sec 1, #15: answer (a), I don't see how that's the assumption the argument relies on. answer E could also work since it also discusses about treatment and a difference in them.

Atlas LSAT Brian
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Re: PT 29 sec 15- LR

Postby Atlas LSAT Brian » Tue May 25, 2010 10:37 am

To spot assumptions, you've first got to analyze the argument.

Premises:
Mountain sickness caused by shortage of oxygen at high altitudes.
Cerebral Edema caused by shortage of oxygen, and life-threatening if not correctly treated.
The symptoms are similar.

Conclusion:
Cerebral Edema especially dangerous at high altitudes.

It's a relatively good argument, I think, which makes it difficult. Easy to see that CE is dangerous. The burning question is: why is CE *especially dangerous* at "high altitudes?"

(A) answers this question. Though the two conditions are similar, the treatment is different. This would make CE especially dangerous at high altitudes because it might be mistaken for mountain sickness, and the wrong treatment given.
Note that if you negate this choice, the conclusion is severely weakened. (ie -- the treatment is the same... now there's no reason to believe that CE is any more dangerous at high altitudes than it is at any other place)

(E) has nothing to do with Cerebral Edema and therefore doesn't matter.

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LSAT Blog
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Re: PT 29 sec 15- LR

Postby LSAT Blog » Tue May 25, 2010 11:16 am

This is a good explanation.

However, it's a bit of an understatement to say that the negation of A causes the argument to be "severely weakened."

I'd go a bit further, and say that if A is negated, the conclusion is destroyed, not just weakened.

If the treatments for cerebral edema and mountain sickness did NOT differ, then it wouldn't really matter whether you mistook one for another. The person with cerebral edema would get the treatment they need regardless of which diagnosis they received (CE or MS).

The necessary assumption MUST be true in order for the conclusion to be true. The conclusion requires it, so someone who believes in the conclusion automatically believes in all necessary assumptions.

If any necessary assumption is not true, the conclusion cannot logically follow.

-Steve

Atlas LSAT Brian
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Re: PT 29 sec 15- LR

Postby Atlas LSAT Brian » Tue May 25, 2010 11:54 am

Naturally, I agree with your comments regarding necessary assumptions.

But if we're splitting hairs, I disagree that this particular conclusion is totally destroyed with the negation of (A). The logic of the argument -- that is, the connection between the similarity of the conditions and the conclusion -- is destroyed, but not the conclusion itself.

My thinking here is that if the conclusion said something like "It is especially dangerous to mistake CE for mountain sickness," then the negation of (A) definitely destroys it. As you wrote:
If the treatments for cerebral edema and mountain sickness did NOT differ, then it wouldn't really matter whether you mistook one for another.

However, mistaking one for the other is not actually the conclusion. And as it is written, the conclusion itself allows room for other, valid reasons for CE to be "especially dangerous" at high altitudes. Perhaps the effects are quickened or worsened at high altitudes. Perhaps treatments at high altitudes are less successful than treatments at lower altitudes.

I completely understand your comments and agree with them in principle, but my feeling is that this example is not actually the best case of a negated assumption "destroying" the conclusion itself, which as you know happens over and over again on this test. In my experience with problems like this, it's better to either say that it destroys the logical connections drawn by the argument, or just say that it really weakens the conclusion.

Thoughts? (and thanks for furthering the discussion!)

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Re: PT 29 sec 15- LR

Postby LSAT Blog » Tue May 25, 2010 12:07 pm

Agreed 100%.

The negation of A destroys the argument in that it destroys the relationship between the evidence and conclusion.

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robotdreams
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Re: PT 29 sec 15- LR

Postby robotdreams » Tue May 25, 2010 2:59 pm

Thank you both Steve and Brian for your input. Both insights were helpful :mrgreen:




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