Understanding Either/Or Statements

[ChicaRosa]

I am confused about the way an Either/Or statement is diagrammed and other inferences from it but with the sentence that says, "Either John or Jack will attend the party." Diagram: John :arrow:Jack, contrapositive: Jack :arrow:John

why is the negation on the sufficient condition side instead of on the necessary condition side in the first diagram? Shouldn't it be: John Jack, contrapositive: Jack John?

Also how does this statement allow the possibility for both John and Jack to attend the party at the same time?

When it comes to using outside knowledge concerning geographical location and height why is the necessary condition negated but not the sufficient condition like the first example?

Thanks!

[Dave Killoran]

Hi Chica,

This blog may help a bit more with your question: http://blog.powerscore.com/lsat/bid/268 ... n-the-LSAT

But, going more deeply into it, the section in the LRB you reference explains this in-depth. Have you read that section closely? That LRB explanation was meant to be definitive, and I'm not certain I can a whole lot more without you first giving me some examples of where you ran into an issue. So, please take a look at that book section again if you don't mind, and then let me know if that makes a bit more sense. If not, we'll work on it some more until you have it down

Thanks!