Example 7 - Summary

Here’s what we learned in this example:

Diagramming Example 7

The argument is diagrammed like this:

7) “If there’s a discipline that can tell us the meaning of life then Ann should major in it because she’s always wondered what the meaning of life might be. But biology studies living things, which means that it can tell us the meaning of life. That’s why Ann should major in biology.”

1. Ann should major in biology.

2. If there’s a discipline that can tell us the meaning of life then Ann should major in it.

3. Ann has always wondered what the meaning of life might be.

4. Biology studies living things

5. Biology can tell us the meaning of life.

3 4

A B

2 + 5

C

1

Notice that:

· The reason indicator expression “because” tells us that idea 3 is being given as a reason to believe idea 2. It corresponds to inference A.

· The inference eraser expression “but” tells us that there probably isn’t an inference between ideas 3 and 4.

· The conclusion indicator expression “which means that” tells us that 4 is being given as a reason to believe 5. It corresponds to inference B.

· The conclusion indicator expression “that’s why” introduces the ultimate conclusion. It corresponds to inference C.

· The premises (ideas 3 and 4) have arrows going from them but no arrows going to them

· The ultimate conclusion (idea 1) has an arrow going to it but no arrow going from it.

· The subconclusions (ideas 2 and 5) have arrows going to them and from them.

Evaluating Example 7

Inference B is weak because 4 doesn’t establish the truth of 5. And this is enough to make the entire argument bad.

7) “If there’s a discipline that can tell us the meaning of life then Ann should major in it because she’s always wondered what the meaning of life might be. But biology studies living things, which means that it can tell us the meaning of life. That’s why Ann should major in biology.”

1. Ann should major in biology.

2. If there’s a discipline that can tell us the meaning of life then Ann should major in it.

3. Ann has always wondered what the meaning of life might be.

4. Biology studies living things

5. Biology can tell us the meaning of life.

3 4 J

A B L

2 + 5 L

C J

1

Let’s do another example.