# GMAT Verbal Section: Critical Reasoning

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This chapter is from the book

### This chapter is from the book 

Terms You Need to Know

• Argument
• Assumption
• Conclusion
• Context
• Critical reasoning
• Discrepancy
• Hypothesis
• Inference
• Phenomenon
• Premise
• Relevance

Concepts You Need to Master

• Applying the scientific method
• Chain of reasoning
• Drawing conclusions/inferences based on information presented
• Identifying evidence and conclusion
• Identifying unwarranted assumptions
• Paraphrasing given material
• Recognizing errors in logic

The GMAT Critical Reasoning questions are meant to test your understanding of arguments and their components. An argument is a conclusion supported by evidence. Each Critical Reasoning question on the GMAT is based on a stimulus argument. (Sometimes there are two questions in a row that are based on a single argument.) The questions reward those who can recognize well-constructed arguments or spot flaws in arguments.

CAUTION

These questions are not knowledge questions. So, take all "facts" at face value and do not answer any questions based on whatever prior knowledge of the subject matter that you may have.

## Argument

There are really only two parts to an argument: evidence and conclusion. A mere statement alone is neither evidence nor conclusion. For example, consider the following statement:

Steve wears glasses.

This statement, without anything more, is simply a statement. We don't know whether it is factual. We don't know whether the author of the statement is going to reason from this proposition toward a further conclusion, or whether this is the ultimate conclusion that the author is trying to support. We need context to determine whether this statement is evidence or conclusion, as follows:

Steve wears glasses.

People who wear glasses are smart.

Therefore, Steve is smart.

In the example, the original statement, "Steve wears glasses," is used as evidence. Note that we are not absolutely sure of the truth of the conclusion because we are not absolutely sure of the truth or falsity of the statement that people who wear glasses are smart. On the other hand, the validity of the argument is unassailable. An argument is valid when its conclusion is well supported by the evidence presented.

Alternatively, the original statement may be supported by evidence rather than used as evidence, as shown in the following example:

Steve is nearsighted.

People who are nearsighted wear glasses.

Therefore, Steve wears glasses.

Again, we are not 100% sure of the truth of the conclusion because at least one piece of evidence is questionable. As we are all aware, not all nearsighted people wear glasses. Some wear contacts; some have surgery. (Some drive very slowly in front of me on the freeway.) However, the argument is valid. And, it illustrates that the original statement, "Steve wears glasses," is neither evidence nor conclusion on its own, and can be either evidence or conclusion, given the proper context.

Note that both of the arguments include two pieces of evidence. This is a minimum for a properly constructed argument. If you try to create an argument with only one piece of evidence, you leave holes, called assumptions. For example

Socrates is a man.

Therefore, Socrates is mortal.

This one has been around for thousands of years. It includes an assumption.

The assumption, or unstated evidence, is that all men are mortal. (In Socrates' case, this was proven beyond doubt by a hemlock cocktail.) So, the complete argument looks like this:

Socrates is a man.

Men are mortal.

Therefore, Socrates is mortal.

We are able to derive the statement "Men are mortal," because it is the only statement that provides a connection between the unlike terms in the original, incomplete argument. Because Socrates appears in both the first piece of evidence and the conclusion, linked to two different words "man" and "mortal," we need a statement linking those two terms.

So, assumptions are important to understanding arguments, in that assumptions are simply unstated evidence.

We all make many assumptions every day. Some are safe or warranted assumptions. Others are a bit shaky. For instance, I can usually safely assume that other drivers on the road are going to stick to the convention of driving on the right side of the road. However, it is less safe to assume that a co-worker has the same political beliefs that I do or even likes the same sports teams.