Critical Reasoning

A drug that is highly effective in treating many types of infection can, at present, be obtained only from the bark of the ibora, a tree that is quite rare in the wild. It takes the bark of 5,000 trees to make one kilogram of the drug. It follows, therefore, that continued production of the drug must inevitably lead to the ibora’s extinction.

Which of the following, if true, most seriously weakens the argument above?
(A) The drug made from ibora bark is dispensed to doctors from a central authority.
(B) The drug made from ibora bark is expensive to produce.
(C) The leaves of the ibora are used in a number of medical products.
(D) The ibora can be propagated from cuttings and grown under cultivation.
(E) The ibora generally grows in largely inaccessible places.

Can someone please explain what is wrong with D. The Oa is E

Not sure where you got those answers from, but your choice is definitely the correct one (and the answer you've stated as correct is defintely wrong).

Its from the 1000SC set. I guess the OA must be wrong then!

could you please explain your answer

D is the correct answer, look in the question stem
"a tree that is quite rare in the wild".
Here the argument makes an assumption that the tree can only grow in wild and not by cultivation.

There are other loop-holes in in argument, such as removing the bark destroys the tree... but they are not mentioned in the answer choices.

E is not the correct answer, as it strengthens on the the premises "a tree that is quite rare in the wild"...

To make the leap from "it takes a lot of trees to make the drug" to "the tree will become extinct", the author has to be assuming that the supply of trees is finite.

To weaken the argument, we look for an alternative to this assumption. Any answer choice that suggests that the supply of trees isn't as limited as the author says will weaken the conclusion.

(D) says that we can grow the tree at tree farms (or greenhouses, or whatever). If we can grow the tree ourselves without touching the trees in the wild, then there's no reason why the tree should become extinct.

Choose (D).

thanks stuart

Stuart Kovinsky wrote:
(D) says that we can grow the tree at tree farms (or greenhouses, or whatever). If we can grow the tree ourselves without touching the trees in the wild, then there's no reason why the tree should become extinct.

Choose (D).

Stuart,

D sounds correct, but E says that the place is inaccessible areas, and conclusion says "continues production", now if the area is inaccessible then the production cannot even continue and therefore weakens the conclusion.

What is wrong in the way I am thinkging?

vineetbatra wrote:

Stuart Kovinsky wrote:
(D) says that we can grow the tree at tree farms (or greenhouses, or whatever). If we can grow the tree ourselves without touching the trees in the wild, then there's no reason why the tree should become extinct.

Choose (D).

Stuart,

D sounds correct, but E says that the place is inaccessible areas, and conclusion says "continues production", now if the area is inaccessible then the production cannot even continue and therefore weakens the conclusion.

What is wrong in the way I am thinkging?

We don't want to argue with the stimulus.

The condition in the conclusion is that if production continues, the tree will become extinct. Even if (e) were a reason why it's difficult to continue production, it wouldn't weaken such a conclusion.

Further, (e) is just too ambiguous. "The Ibora generally grows in largely inaccessible places" isn't strong enough to allow us to conclude that "there are trees that are wholly inaccessible and therefore production won't lead to extinction".

[quote="Stuart Kovinsky
We don't want to argue with the stimulus.

The condition in the conclusion is that if production continues, the tree will become extinct. Even if (e) were a reason why it's difficult to continue production, it wouldn't weaken such a conclusion.

quote]
Thanks for the response Stuart, what I understand of a weakening question is either one can target the conclusion/premise directly, or bring in new information that will target conclusion/premise.

Production cannot continue because Ibora generally grows in areas that are largely inaccessible. So if the trees cannot be reached then the trees cannot be used to create drug, so if no producion then extinction because of production.


So I am directly targeting the conclusion itself.

Hope I am able to explain my difficulty/reasoning clearly.

[quote="vineetbatra]Thanks for the response Stuart, what I understand of a weakening question is either one can target the conclusion/premise directly, or bring in new information that will target conclusion/premise.

Production cannot continue because Ibora generally grows in areas that are largely inaccessible. So if the trees cannot be reached then the trees cannot be used to create drug, so if no producion then extinction because of production.


So I am directly targeting the conclusion itself.

Hope I am able to explain my difficulty/reasoning clearly.[/quote]

You're correct in your general reasoning - one way to weaken is to directly cast doubt on the conclusion.

You're reading the conclusion as "the ibora will become extinct". The problem with your analysis is that the conclusion is actually "continued production will lead to the ibora becoming extinct".

Accordingly, we don't need to worry about production stopping, since continued production is a precondition of the author's conclusion even being relevant.

Let's examine an analagous (and more straightforward) statement:

"If I eat too much ice cream, I'll get fat."

Let's say we wanted to weaken this prediction. The equivalent to (e) would be:

"The store is out of ice cream",

a reason why we don't have to worry about eating ice cream in the first place. The equivalent to (d) could be:

"I can exercise more to burn off the extra calories from the ice cream",

which provides an alternative to getting fat.

The store being out of ice cream doesn't weaken the prediction, because the prediction is based on the condition "if I eat ice cream"; the actual availability of ice cream is irrelevant to the situation.

Of course, as I stated in my earlier post, the above issue isn't the only one with (e). In fact, a better equivalent for (e) would be:

"some stores might be out of ice cream",

which clearly doesn't weaken the prediction at all.

Thanks Stuart, that was a good explanation, now I understand the flaw in my reasoning.

Vineet

Stuart wrote:

You're correct in your general reasoning - one way to weaken is to directly cast doubt on the conclusion.

You're reading the conclusion as "the ibora will become extinct". The problem with your analysis is that the conclusion is actually "continued production will lead to the ibora becoming extinct".

Accordingly, we don't need to worry about production stopping, since continued production is a precondition of the author's conclusion even being relevant.

Let's examine an analagous (and more straightforward) statement:

"If I eat too much ice cream, I'll get fat."

Let's say we wanted to weaken this prediction. The equivalent to (e) would be:

"The store is out of ice cream",

a reason why we don't have to worry about eating ice cream in the first place. The equivalent to (d) could be:

"I can exercise more to burn off the extra calories from the ice cream",

which provides an alternative to getting fat.

The store being out of ice cream doesn't weaken the prediction, because the prediction is based on the condition "if I eat ice cream"; the actual availability of ice cream is irrelevant to the situation.

Of course, as I stated in my earlier post, the above issue isn't the only one with (e). In fact, a better equivalent for (e) would be:

"some stores might be out of ice cream",

which clearly doesn't weaken the prediction at all

Although I agree to Stuart, I think E is a strong contender, infact is the right answer.

Two reasons:
1) Concl: if you continue production, the world will run out of the bark.
D says -> We can graft and produce more and don't have to depend on its natural existence and growth - Yes weakens, but you need to assume here that 'grafting and producing these could keep up with the pace and not having to loose all these grafted shoots leading to extinction'. E says no matter what you will never run out of them.

2) The example Staurt chose is slightly misleading imo. The correct parallel to the simple example should be something to the extent of
"If I eat too much ice cream, my home will run out of ice cream"
D: I replace the ice cream every thursday
E: Some of the ice cream has managed to find its way to places I can never get to in my home.

The question asks for 'most seriously weakens' so even though both D and E weaken, E does not require any assumptions and does it more seriously.

Stuart help us here...I could be missing something.