Let's assume that you are working on a weaken question. We are trying to undermine the conclusion.
Our first step is to identify that conclusion. Let's take a simple argument:
John is tall. Accordingly, he must be good at basketball.
The blue statement is the conclusion. Once we know the conclusion, we can ask the question why? Because John is tall. But our job is to weaken the conclusion.
You seem to be asking whether we could dispute the idea that John is tall. How tall is he? Maybe he's only 5'11. Is that really tall? However, these types of considerations will not be part of a GMAT argument.
The GMAT argument will revolve around the assumption. In this case the assumption is: Tall people are good at basketball. We know that this is the assumption because the conclusion mentions basketball, but the premise only talks about John's height. The assumption will connect the premise to the conclusion.
In order to weaken the argument, we will be trying to attack that assumption. How can we do so?
One way is to simply have a statement that negates the assumption. One example may be "Not all tall people are good at basketball." Another way may be to show that the cause does not always lead to the effect. A statement such as "Carlos is taller than John, but he's terrible at basketball" would suffice.
Here's a real example:
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.
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What's the conclusion? It is: Continued production of the drug will lead to the ibora's extinction.
Why? Because A) the drug can only be obtained from the bark of the ibora and b) the ibora is quite rare in the wild.
What's the assumption? That wild ibora trees are the only source of ibora bark. Accordingly, to weaken, we will need to find some other source of ibora bark than wild ibora trees. Answer choice (D), the credited response, does so.
The best answer will never be something like: Ibora trees are actually quite common in the wild or It actually takes the bark from only one ibora tree to make the drug.
Elias Latour
Verbal Specialist @ ApexGMAT
blog.apexgmat.com
+1 (646) 736-7622
