Inductive and Deductive Reasoning

Deductive and Inductive Arguments: Two Ways of Understanding

We have two basic ways of reasoning to determine whether something is true: deductive reasoning and inductive reasoning.

Deductive Reasoning: From General to Specific

Deductive reasoning starts with a general principle (premises) assumed to be true and determines what must logically follow. If the premises are correct, the conclusion is guaranteed to be true (in other words, you can provide absolute proof of your conclusions). However, the premises themselves are often unproven, or sometimes unprovable.

Inductive Reasoning: From Specific to General

Inductive reasoning moves in the opposite direction—it begins with specific observations and uses them to form a general conclusion. By identifying patterns, we infer a broader principle that explains the data.

However, unlike deduction, induction does not prove a theory—it only suggests a likely (or probable) explanation. Alternative explanations may exist, and additional evidence is needed to confirm the conclusion.

The key to inductive reasoning is ensuring that the conclusion logically explains the data. A conclusion that ignores relevant evidence or contradicts observations would not be logically sound.

Example: Deductive vs Inductive reasoning

Here is an example of how you might reach a conclusion differently if you are applying deductive or inductive reasoning.

Deductive Reasoning

• You read in the news that this grocery store has a tradition of employees wearing football jerseys on Fridays.

• Today is Friday.

• You go to the grocery store.

• The clerks are wearing football jerseys.

Because you started with a general rule and applied it to a specific case, you deduce that the clerks wear football jerseys on Fridays to support the local team.

Inductive Reasoning

You visit your local grocery store every day.

• Two weeks ago, on Friday, the clerks wore football jerseys.

• Last Friday, they wore them again.

• Today, another Friday, they are also wearing jerseys.

Based on these observations, you induce that the clerks wear football jerseys every Friday to support the local team.

Deduction and induction by themselves are inadequate to make a compelling argument. While deduction gives absolute proof, it never makes contact with the real world, there is no place for observation or experimentation, and no way to test the validity of the premises. And, while induction is driven by observation, it never approaches actual proof of a theory. Therefore an effective paper will include both types of logic.

Adapted from "Inductive vs. Deductive Reasoning" by Lumen Learning. Licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).