Which one of the following is an acceptable selection of animals for the study?

Jerome June 19, 2020

What's the difference between NOT BOTH and EITHER OR?

I wanted to know what the difference between NOT BOTH and EITHER OR was. In In and Out Games, it seems that NOT BOTH implies that 1 of a pair needs to be out and EITHER OR implies that 1 of a pair needs to be in; what is the significance of being in or out? Could I see it as one needs to be in and the other needs to be out, that way I could treat the wording of both the same?

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Skylar June 19, 2020

@Jerome, happy to help!

These two phrases are an important concept on the LSAT, but they are not treated the same. I find it helpful to focus on the necessary conditions as an indicator of what is possible. Here, "in" refers to being selected and "out" refers to not being selected."

"Not both"
A -> not B
B -> not A
This means that at least one of A and B must be out, and it is possible that both could be out.

"Either or"
Not A -> B
Not B -> A
This means that at least one of A and B must be in, and it is possible that both could be in.

Does that make sense? Hope it helps! Please let us know if you have any other questions!

Jerome June 26, 2020

Hi Skylar!

Thanks for that. In this case, why do we use them in a similar fashion where if one isn't in then the other one is out? With NB either one of them is out but both could we out, so why would we substitute in one if the other was out? The same seems to happen with EO premises.