Introduction to Critical Reasoning

Critical-reasoning questions are essentially logic problems based in the context of an argument. A paragraph is presented, usually one in which a claim is made based on given information, and you must answer a logic question related to the paragraph (e.g., “What would weaken the argument?” “What is an assumption on which the argument is based?” etc.)

To properly analyze arguments, it helps to know what the components of an argument are. The parts of an argument determine the strategies for the various types of questions.

Parts of an Argument

An argument consists of four main parts:

1. Premise- a fact that is presented in support of the conclusion

2. Conclusion- the written claim that the author wants you to believe

3. Assumption- a statement that is not written and on which the conclusion relies

4. Inference- a statement that must be true if everything written is true

The parts that are written are the premises and the conclusion (unless the question is a conclusion question in which you are presented only with a list of facts). Generally, though, the author presents some premises (a.k.a., facts, premises, evidence, general patterns, etc.) in support of a written claim (the conclusion) that may or may not be true.

The parts of the argument that are not written are the assumptions and inferences. Assumptions are missing statements on which the conclusion relies; they are the missing link between the premises and conclusion. The conclusion is valid only as long as the assumptions are true. The fourth part of an argument is the inference, a statement that is not written but that must also be true if everything written, including the conclusion, is true.

Note: All critical reasoning questions, unless they are conclusion or inference questions, affect the validity of the conclusion.

Regardless of whether you are required to weaken the argument, strengthen the argument, find the assumption, identify the flaw, or resolve the paradox, the answer makes the conclusion (not the premises) more or less believable. It is, therefore, important to identify the sentence that is the conclusion and be sure not to counter any of the premises that were presented.

The following are key words that can help you identify the conclusion in an argument:

General: so, hence, therefore, thus, if…, then
Advice: should, must, ought to
Indication: indicates that, suggests that, claims that
Prediction: will, would
Over confidence: clearly, obviously, evidently, indubitably
Conflict: nonetheless, nevertheless, however, regardless, but, yet
 

Argument Types
There are three main argument types in critical reasoning:

1. Causal Arguments 

A causal argument is an argument in which the author wants you to believe that some event or factor (A) caused some other event (B).

Example: Sandra took a GMAT course at the Best Prep test-preparation school.  She then got a 750 on the GMAT.  Therefore, Best Prep was responsible for Sandra’s high score.

Premise 1: Sandra took a GMAT course at the Best Prep test-preparation school.

Premise 2: She then got a 750 on the GMAT. 

Conclusion: Therefore, Best Prep was responsible for Sandra’s high score.

Assumption:  Nothing other than A was responsible for/affected/caused B. (For example: Nothing other than the course was responsible for Sandra’s high score.)

To weaken: Offer an alternative cause for B. (For example: Sandra is possesses unparalleled genius, especially when it comes to taking high-stress adaptive exams.)

To strengthen: Eliminate an alternative cause OR explain how A lead to B. (For example: Sandra is not the sharpest pencil in the box, so to speak.)

2. Arguments by Analogy 

An argument by analogy is one in which the author wants to believe that what happened to some party (A) will also happen to another party (B).

Example: Dan took a GMAT course at the Best Prep test-preparation school.  He then got a 750 on the GMAT.  Therefore, if Sara takes the Best Prep GMAT course, she will get a high score.

Premise 1: Dan took a GMAT course at the Best Prep test-preparation school.

 Premise 2: Dan then got a 750 on the GMAT. 

 Conclusion: Therefore, if Sara takes the Best Prep GMAT course, she will get a high score.

 Assumption:  A is similar to B. (Dan is similar to Sara.)

To Weaken: Show how A is different from B. (For example: Unlike Dan, Sara has studied nothing other than computer engineering for the past five years.) 

To Strengthen: Show how A is similar to B. (For example: Sara and Dan are equally strong in mathematics.)

3. Statistical Arguments

A statistical argument is one in which the author wants you to believe that some sample group is representative of a larger group.

Example: 70% of test-takers who took the Best Prep GMAT course and received above a 700 on the GMAT attributed their success to Best Prep in a voluntary survey.  Therefore, Best Prep is an effective test-preparation school.

Premise 1: 70% of test-takers who took the Best Prep GMAT course and received above a 700 on the GMAT attributed their success to Best Prep in a voluntary survey. 

Conclusion: Therefore, Best Prep is an effective test-preparation school.

Assumption:  The sample group is representative.

To Weaken: Show how the sample group is not representative. (For example: questioning who, where, when, and base number of respondents casts doubt on whether the sample group is representative.)

To Strengthen: Show how the sample group is representative. (For example: The vast majority of Best Prep students received above 700.)

Now you are ready to learn the question types and strategies!