Question

*find and post examples of deductive and inductive arguments.
*for each example, evaluate its logical strength

Answer 1

Solution:-

Can you see the different ways the premises support the conclusion in the following arguments?

Deductive
All philosophers have a brain.
Bob is a philosopher.
Therefore, Bob has a brain.

Inductive
Most philosophers have a brain.
Sam is a philosopher.
So, Sam probably has a brain.

This distinction describes how the premises support the conclusion. In deductive arguments, the truth of the premise(s) guarantees the conclusion. That is, it is impossible for the conclusion to be false if we assume the premises are true in a good/valid deductive argument.

In inductive arguments, the premise(s) provide probabilistic support. That is, it is improbable, but possible, that the conclusion is false in good/strong inductive arguments.

Argument 1 is a deductive argument because the conclusion must follow if we assume the premises are true. In example 1, it is impossible for the conclusion (i.e. Bob has a brain) to be false if the premises are assumed true. So, it is a valid deductive argument.

In Argument 2, it’s improbable that the conclusion is false if we assume the premises are true. It’s possible, but unlikely, that Sam doesn’t have a brain.

In short, deductive and inductive refer to how the arguer is claiming the premises support the conclusion. In a deductive argument, the arguer is claiming the conclusion must follow if we assume the premises are true. In an inductive argument, the arguer is claiming the conclusion probably follows if we assume the premises are true.

Many websites present misconceptions about deduction and induction, which include the following:

Misconception 1: Deductive arguments always move from general to specific whereas inductive arguments move from specific to general.

Correction: Actually, some deductive arguments move from specific to general claims, and some inductive arguments move from general to specific. I will provide some examples in the activity.

Misconception 2: Deductive arguments are based on facts. Inductive arguments aren’t.

Correction: Actually, the truth of the premises has nothing to do with whether an argument is deductive or inductive. Rather, deduction and induction is all about how the arguer claims the premises support the conclusion if we assume the premises are true. Both deductive and inductive arguments can have false premises.

Misconception 3: Science is only about inductive thinking.

Correction: Actually, science uses both inductive and deductive thinking. I will illustrate in the exercise.

Before concluding, I should emphasize one final clarification. Deductive and inductive refer to how the arguer is claiming the premises support the conclusion. For example, the following is a deductive argument because I am claiming the conclusion must follow if the premises are assumed true:

All whales are mammals.

Shamu is a mammal.

So, Shamu is a whale.

This argument is deductive because I am claiming the conclusion must follow. But, of course, the conclusion does not follow even if we assume the two premises are true, so it is an invalid deductive argument. Just because x is a mammal and "all whales are mammals" does not mean it must be the case that "x is a whale." X could be a nonwhale mammal, like a cat.