Bug in PT C S2 Q#2

jim-green
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Bug in PT C S2 Q#2

Postby jim-green » Wed May 04, 2011 11:14 am

The question makes the following conclusion: I should stop drinking; only then will I not get cancer.
Ensure no cancer ---> Stop drinking

TCR is E, which says "does not consider possibility of other causes of cancer."

However, the conclusion does not say stopping drinking will ensure no cancer. It says stop drinking is a must to get no cancer. It does not exclude other causes. It just says if you don't stop drinking, you cannot ensure no cancer. The word "only" in the stim is a bug in the question.

kehoema2
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Re: Bug in PT C S2 Q#2

Postby kehoema2 » Wed May 04, 2011 11:21 am

jim-green wrote:The question makes the following conclusion: I should stop drinking; only then will I not get cancer.
Ensure no cancer ---> Stop drinking

TCR is E, which says "does not consider possibility of other causes of cancer."

However, the conclusion does not say stopping drinking will ensure no cancer. It says stop drinking is a must to get no cancer. It does not exclude other causes. It just says if you don't stop drinking, you cannot ensure no cancer. The word "only" in the stim is a bug in the question.


Pretty sure the diagram is

~drinking --> ~cancer

That should answer your question.

jim-green
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Re: Bug in PT C S2 Q#2

Postby jim-green » Wed May 04, 2011 11:39 am

kehoema2 wrote:
jim-green wrote:The question makes the following conclusion: I should stop drinking; only then will I not get cancer. Ensure no cancer ---> Stop drinking
TCR is E, which says "does not consider possibility of other causes of cancer."
However, the conclusion does not say stopping drinking will ensure no cancer. It says stop drinking is a must to get no cancer. It does not exclude other causes. It just says if you don't stop drinking, you cannot ensure no cancer. The word "only" in the stim is a bug in the question.
Pretty sure the diagram is
~drinking --> ~cancer That should answer your question.
Your diagram would be correct if the stim said, "You don't get cancer if you don't drink." However, the stim says, "You don't get cancer only if you don't drink." Hence: ~cancer --> ~drinking

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510Chicken
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Re: Bug in PT C S2 Q#2

Postby 510Chicken » Wed May 04, 2011 12:39 pm

jim-green wrote:
kehoema2 wrote:
jim-green wrote:The question makes the following conclusion: I should stop drinking; only then will I not get cancer. Ensure no cancer ---> Stop drinking
TCR is E, which says "does not consider possibility of other causes of cancer."
However, the conclusion does not say stopping drinking will ensure no cancer. It says stop drinking is a must to get no cancer. It does not exclude other causes. It just says if you don't stop drinking, you cannot ensure no cancer. The word "only" in the stim is a bug in the question.
Pretty sure the diagram is
~drinking --> ~cancer That should answer your question.
Your diagram would be correct if the stim said, "You don't get cancer if you don't drink." However, the stim says, "You don't get cancer only if you don't drink." Hence: ~cancer --> ~drinking

You're actually both correct. The statement "If I (I should) stop drinking, only then will I not get cancer" is a biconditional, which means that both sides of the conditional statement are necessary and sufficient for the other. You can see this from the statement. If the dude stops drinking, then he will not get cancer. If the dude doesn't get cancer, then he must have stopped drinking (because of "only"). The statement can best be rewritten as "If I stop drinking, then, and only then, will I not get cancer". The first "then" is actually omitted by the stimulus, but it is implied by the second. Sometimes English can be a bitch.

As a result, the statement actually does say that stopping drinking is sufficient to avoid cancer, which the correct answer indicates is probably an unwarranted assumption.

EDIT: For the future, I would always assume that the Official LSAT answer is correct and that you are doing something wrong (and I don't mean that harshly at all. Obviously, preparing for the LSAT is a learning process). A PT is not a low end Kaplan text. Real time and effort gets put into developing the questions/answers.

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suspicious android
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Re: Bug in PT C S2 Q#2

Postby suspicious android » Wed May 04, 2011 1:42 pm

510Chicken wrote:You're actually both correct. The statement "If I (I should) stop drinking, only then will I not get cancer" is a biconditional, which means that both sides of the conditional statement are necessary and sufficient for the other. You can see this from the statement. If the dude stops drinking, then he will not get cancer. If the dude doesn't get cancer, then he must have stopped drinking (because of "only"). The statement can best be rewritten as "If I stop drinking, then, and only then, will I not get cancer". The first "then" is actually omitted by the stimulus, but it is implied by the second. Sometimes English can be a bitch.


Eh, I don't think it's fair to assume it's a biconditional just because that would make TCR make sense. Clearly "then and only then" would indicate bicondionality. But it just says "only then", which by itself can only reliably be said to indicate a necessary condition The bolded part of your statement above is just asserted, not supported. How does either the context or the syntax suggest that?

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suspicious android
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Re: Bug in PT C S2 Q#2

Postby suspicious android » Wed May 04, 2011 1:59 pm

The stimulus says "only then will I be sure not to develop bone cancer".

How might it be different it the guy had said: "only then will I be safe from this threat". That would be a valid argument, no? I think the key here is the idea that this will make him sure not to develop bone cancer, since as (E) suggests, there are other causes of bone cancer.

jim-green
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Re: Bug in PT C S2 Q#2

Postby jim-green » Wed May 04, 2011 2:14 pm

Haha!
510Chicken wrote:A PT is not a low end Kaplan text. Real time and effort gets put into developing the questions/answers.

jim-green
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Re: Bug in PT C S2 Q#2

Postby jim-green » Wed May 04, 2011 2:28 pm

510Chicken wrote:You're actually both correct. The statement "If I (I should) stop drinking, only then will I not get cancer" is a biconditional, which means that both sides of the conditional statement are necessary and sufficient for the other.
Thanks, the more I think about it, the more I see vous etes just. "If A, only then B" means "Iff A then B."
If A then B : A->B
A only if B : a->B
If A, only then B. A<->B

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510Chicken
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Re: Bug in PT C S2 Q#2

Postby 510Chicken » Wed May 04, 2011 2:32 pm

suspicious android wrote:Eh, I don't think it's fair to assume it's a biconditional just because that would make TCR make sense. Clearly "then and only then" would indicate bicondionality. But it just says "only then", which by itself can only reliably be said to indicate a necessary condition The bolded part of your statement above is just asserted, not supported. How does either the context or the syntax suggest that?


I see... I would be more inclined to agree with you were the statement "only if". However, I think "only then" implies a result (and thus the first "then" in the biconditional). It's a phrase you use when you only need one more thing, hence the "then" component.

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suspicious android
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Re: Bug in PT C S2 Q#2

Postby suspicious android » Wed May 04, 2011 2:38 pm

510Chicken wrote:I see... I would be more inclined to agree with you were the statement "only if". However, I think "only then" implies a result (and thus the first "then" in the biconditional). It's a phrase you use when you only need one more thing.


Definitely "only if", and I was thinking the same as you about "only then" just to try to make sense of this question. However, I don't think that by itself "only then" really indicates biconditionality. For example:

After you're 16 you can get a driver's license, only then can you legally drive.

Wouldn't you agree that statement is not a biconditional? Clearly some older people cannot legally drive, but that doesn't contradict the statement.

jim-green
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Re: Bug in PT C S2 Q#2

Postby jim-green » Wed May 04, 2011 2:42 pm

suspicious android wrote:After you're 16 you can get a driver's license, only then can you legally drive.
After you're 16, only then can you legally apply for a driver's license.

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suspicious android
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Re: Bug in PT C S2 Q#2

Postby suspicious android » Wed May 04, 2011 2:49 pm

jim-green wrote:After you're 16, only then can you legally apply for a driver's license.


Same deal, convicted criminals have to wait until they're 18.

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510Chicken
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Re: Bug in PT C S2 Q#2

Postby 510Chicken » Wed May 04, 2011 3:12 pm

suspicious android wrote:
510Chicken wrote:I see... I would be more inclined to agree with you were the statement "only if". However, I think "only then" implies a result (and thus the first "then" in the biconditional). It's a phrase you use when you only need one more thing.


Definitely "only if", and I was thinking the same as you about "only then" just to try to make sense of this question. However, I don't think that by itself "only then" really indicates biconditionality. For example:

After you're 16 you can get a driver's license, only then can you legally drive.


Wouldn't you agree that statement is not a biconditional? Clearly some older people cannot legally drive, but that doesn't contradict the statement.


Well first, I don't think the analogy is particularly apt. It breaks down to "if 16 --> can get license --> can legally drive", which is kind of my point. The license is the final barrier to legally driving, which does make it biconditional. Driving requires a license. Getting a license allows you drive since implicitly all other conditions (being 16) have been met.

Second, older people who can't legally drive satisfy this too. There may be a variety of reasons that they are no longer capable of driving (eyesight, reaction speed, etc), but ultimately this culminates in their licenses not being renewed.
"Can see, can hear --> license --> legally drive" ... "~can see, ~can hear --> ~license --> not legally drive"

suspicious android wrote:
jim-green wrote:After you're 16, only then can you legally apply for a driver's license.


Same deal, convicted criminals have to wait until they're 18.

...but different from the original statement since it contradicts the first conditional "if 16 --> can get license"

I mean, I understand what you're trying to say, but I think that whenever I only want a necessary condition, I'll use "only if" and reserve "only then" for the biconditional. Which is admittedly circular, but any definition kinda is.

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suspicious android
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Re: Bug in PT C S2 Q#2

Postby suspicious android » Wed May 04, 2011 3:26 pm

510Chicken wrote:I mean, I understand what you're trying to say, but I think that whenever I only want a necessary condition, I'll use "only if" and reserve "only then" for the biconditional. Which is admittedly circular, but any definition kinda is.


Yeah, that's the point at issue. I can kinda see the idea that you use the phrase "only then" when you are isolating a necessary condition that is also the only necessary condition unmet. However, that would mean that the phrases "only then" and "then and only then" are logically identical, which makes me uncomfortable. This phrase can be used in any number of ways, few of which make it clear to me that both conditions are necessary and sufficient.

It will be warm in spring, only then will the strawberries grow.

Well, there are obviously many other things that strawberries require to grow, but is the above sentence really implying that all other conditions are met? I'm skeptical, but perhaps this is a situation where the commonsense interpretation is the correct one.

jim-green
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Re: Bug in PT C S2 Q#2

Postby jim-green » Wed May 04, 2011 4:19 pm

Fellows, here is my latest thought. The relation between drinking and cancer is sufficient, i.e., if drinking, then cancer. John's flaw is that he assumes it is bi-conditional. He thinks drinking is necessary. So he says if i don't drink, then no cancer. That is the flaw in and E. The relationship is not bi-conditional. It is only one way. That is the flaw E describes.




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