Example 4 - Summary

Here’s what we learned in this example:

Inference Eraser Expressions

Inference eraser expression show that an inference isn’t present between two ideas, that neither idea is being given as reason to believe the other. Inference eraser expressions are “and” (including equivalent expressions like “moreover,” and “furthermore”) and “but” (including equivalent expressions like “however,” and “nevertheless.”)

Diagramming Example 4

Our argument is diagrammed like this:

4) “Ann should major in history since her parents want her to and people should major in whatever their parents want them to.

1. Ann should major in history.

2. Ann’s parents want her to major in history.

3. People should major in whatever their parents want them to.

2 + 3

A

1

Notice that

· The reason indicator expression “since” introduces reasons in the passage.

· The inference eraser expression “and” shows that there is no inference between 2 and 3.

· 2 and 3 are added together in the diagram because we need them to work together to support 1.

Evaluating Example 4

Our argument is evaluated like this:

1. Ann should major in history.

2. Ann’s parents want her to major in history.

3. People should major in whatever their parents want them to.

2 J + 3 L

A J L

1

Notice how the inference is good even though premise 3 is false.

The inference is strong because if Bob believed 2 and 3, he’d be forced to believe 1 as well.

Let’s work through another example.