We have learned how to divide an argument into premises and a conclusion. While splitting the argument, you should watch out for the order in which premises are stated. A common deductive fallacy seen in Critical reasoning question is when the premises and conclusions are true but invalid. The test taker evaluates them separately and finds truth in the statements, thus assuming that truth equals validity. This is not the case, and test creators are using ‘Affirming the Consequent’ fallacy to trap the GMAT test taker.
What is affirming the Consequent?
If ‘A’ & ‘B’ represent the statements, the affirming the consequent fallacy will be structured in the following format:
Premise 1: If A, then B
Premise 2: B
The format is easy to miss since statement B would be true, and Premise 1 follows the logical structure (If A then B). Premise 1 becomes the base of the argument, and test takers often doesn’t consider additional conditions apart from ’ A’ or order of the statement presented in the premise.
To understand the fallacy, let us look at a common example used in GMAT tests.
Premise 1: If Ron scores 720 in GMAT Exam, he will get into Harvard
Premise 2: Ron got into Harvard
Conclusion: Ron scored 720 in GMAT Exam
The fallacy is easy to miss. Pay attention to premise 1 and how “If A then B” statement is framed.
Test takers assume that the score is a pre-condition for getting into Harvard, and that is where the fallacy misguides them in picking the wrong answer choice. Ron can get into Harvard by scoring any score ranging from 720 to 799. Therefore making hasty conclusions based on one condition is false.
How to overcome ‘Affirming the Consequent’ fallacy
1) When you see conditions of the format If A then B, check and see if B can be caused by conditions other than A
2) Whenever Premise 2 is a statement, it is likely that the test creator would use the statement to make a faulty conclusion.
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