Defender Assumption Question

[tessajw]

Hi,
I am currently on the lecture explaining the defender assumption questions.
The following stimulus was used as an example:

"People who read a lot are more intelligent than other people. Thus, reading must cause a person to be intelligent."

And then the prompts giving examples of correct answers are :
"Regular exercise does not cause a person to be intelligent"
"Genetics do not cause a person to be intelligent"

I just don't understand at all how these assumptions have anything to do with being necessary to assume to prove the conclusion.

The conclusion does not say that reading is the only possible cause of intelligence and nothing else can contribute to a person being intelligent. It just says that reading must cause a person to be intelligent. Meaning that if a person reads, it causes them to be intelligent. Why does that mean it's assumed that all other things on earth cant also cause intelligence? It doesn't say that nothing else ever causes intelligence, so I don't understand how one would logically infer that assumption, if the conclusion is not exclusive to reading, it's just stating one cause of intelligence.

Please explain.

[Dana D]

Hey Tessajw,

For cause and effect conditional logic, the stated cause must be the only cause of the effect. In this case, if the argument says reading causes a person to be intelligent, we must assume that no other factors cause a person to be intelligent. This is how the LSAT treats cause and effect arguments, which I understand is different from how we might use them in regular daily life. Because only 1 cause can bring about the 1 effect, we must assume that any other possible causes do not actually bring about intelligence - that is why these examples are used as defender assumptions. They help defend our argument against possible ways to weaken it.

I would suggest reviewing the lessons on cause and effect arguments in order to better understand this concept if it's still giving you trouble! Hope that helps.