Types of Reasoning: Deductive and Inductive

Each logical argument has premises and a conclusion, but not every argument comes to a conclusion in the same way. For the purposes of the GMAT, you should be familiar with two basic types of logical reasoning: deductive and inductive.

Deductive Reasoning

In deductive reasoning, you come up with a specific conclusion from more general premises. The great thing about deductive reasoning is that if the premises are true, the conclusion must be true. In deductive reasoning, the conclusion must be true if the premises are true.

When you analyze deductive reasoning arguments for the GMAT, the only way you can prove that a conclusion is true is by showing that all premises are true. The only way to prove that a deductive reasoning conclusion is false is to show that at least one of the premises is false.

Inductive Reasoning

In deductive reasoning, you draw a specific conclusion from general premises. With inductive reasoning, you do the opposite - you develop a general conclusion from specific premises. Inductive reasoning differs from deductive reasoning in that the conclusion in an inductive reasoning argument could be false even if all the premises are true.

With inductive reasoning, the conclusion is essentially your best guess. That’s because an inductive reasoning argument relies on less complete information than deductive reasoning does.

Analogy Arguments

An analogy argument tries to show that two or more concepts are similar so that what holds true for one is true for the other. The strength of the argument depends on the degree of similarity between the persons, objects, or ideas being compared.

Cause-and-effect Arguments

A cause-and-effect argument concludes that one event is the result of another. These types of arguments are strongest when the premises prove that the alleged cause of an event is the most likely one and that no other probable causes exist.

Statistical Arguments

Arguments based on statistical evidence rely on numbers to reach a conclusion. These types of arguments claim that what’s true for the statistical majority is also true for the individual. But because these are inductive reasoning arguments, you can’t prove that the conclusions are absolutely true. When you analyze statistical arguments on the GMAT, focus on how well the given statistics apply to the circumstances of the conclusion.

To do well on the critical reasoning questions, you need to recognize premises and conclusions in arguments, determine whether the argument applies deductive or inductive reasoning (most will be inductive), and, if the argument is inductive, figure out the method the author uses to reach the conclusion.