Isolating the Nerve Center of an Argument
Arguments in real life can take a number of forms, but arguments on GMAT Critical Reasoning questions are relatively formulaic. The typical GMAT argument has three parts:
1) Premise: the starting point of deductions; often, agreement to this is assumed.
2) Conclusion: what the author wants you to believe by the end of the argument
3) Assumption: the unstated link between premise and conclusion.
Although unstated, the assumption is the nerve center of the argument, the linchpin holding the whole thing together.
Strengthening and Weakening Arguments
Assumptions are crucial in understanding an argument, and because of this, they play a large role in two major Critical Reasoning question types. Some questions ask you: "Which would most strengthen the argument?" The most powerful way to strengthen an argument is to validate its assumption. Other questions, perhaps the single most common on Critical Reasoning, ask: "Which of the following would most weaken the argument?" The most devastating attack on an argument is the denial of its assumption --- without the assumption, the link between the premise and the conclusion is severed.
Think Broadly
When identifying assumptions, one crucial point to remember: assumptions are most often general statements, not specific statements. If my premise is "Fred has quality A," and my conclusion is "Therefore, Fred has quality B," then the assumption is not going to involve Fred at all. The assumption would be something like "most/all folks who have quality A also have quality B." In trying to identify the assumption, it can helpful to remember that you can omit any specific people/places/items mentioned.
Identifying the Assumption
Consider, first of all, this relatively ludicrous argument:
Hawaii is a place with beautiful scenery. Therefore, people there must have trouble concentrating for any length of time at all.
The premise: Hawaii is a place with beautiful scenery --- we can safely assume that at least 99 out of a hundred peoplewould agree with that! The wacky conclusion: people there can't concentrate. The assumption must provide a link.
Hawaii is the specific, so drop that. The premise has to do with "place with beautiful scenery", and the conclusion has to with "trouble concentrating", so just put those together with a strong logical connection: "People in places with beautiful scenery generally have trouble concentrating." There! That's a possible way to state the assumption. It would most strengthen this laughable argument if one could somehow provide data or evidence supporting this assumption. It would shatter this poor argument if we could cite data or evidence that directly contradicts the assumption.
Now, consider a somewhat more GMAT-worthy argument:
Of all the companies in the steel industry in the last six months, only Amalgamated Ferric Industry (AFI) has tripled their advertising expenditures. No other steel company has increased advertising nearly that much.Therefore, in the coming months, we should see AFI gaining new customers at a race that outpaces all its competitors.
Dropping the specifics, the premise is about increasing spending on advertising, and the conclusion is: more new customers. An assumption would link these. A very broad assumption: "companies that increase what they spend on advertising generally see an increase in new customers." A slightly more specific assumption: "when companies in the steel industry increase advertising, this generally results in more new customers." This is a relatively poor argument, and if we were asked for a statement to weaken it, the best choice would be something that zeroed in on the assumption. For example: studies of companies in the steel industry show little correlation between advertising dollars and new customers. That strikes right at the nerve center of the argument, obliterating it. That's exactly what this kind of GMAT Critical Reasoning is asking you to do.
On the real GMAT, if you can anticipate what the best answer choice will look like, that will make it much easier to find!
Here are two Critical Reasoning practice questions to practice your assumption skills:
https://gmat.magoosh.com/questions/1272
https://gmat.magoosh.com/questions/1261
This post was written by Mike McGarry, GMAT Expert at Magoosh, and originally posted here.
