Either/Or Diagramming

[JG350]

I am trying to practice my diagramming, and I am running into a pretty basic problem. I am not able to understand why certain statements (examples below) are represented certain ways:
5 Lb Book, P. 63, #11: Either Tony or Angela is in charge of the house (diagrammed in the book as -TC [right arrow] AC. Contrapositive: -AC [right arrow] TC.)
5 Lb Book, P. 64, #30 Either giraffes will take over the world or bonobos will (diagrammed in the book as -GTOW [right arrow] BTOW. Contrapositive: -BTOW [right arrow] GTOW.).

Why is it diagrammed as the negative of something causes the positive of something else, as opposed to the positive of something causing the negative of something else?

Best,
J

[ohthatpatrick]

I think it's actually highly arbitrary how they're choosing to show the "right answer".

We would need more context on the rules / parameters of the game to really know how we want these to look.

There's an important ambiguity to #11 and #30:

#11 - "either Tony or Angela is in charge of the house"

- Can they BOTH be in charge of the house?
- Can they BOTH take over the world?

On LSAT, we interpret "or" and "either/or" to be inclusive (meaning "at least one"), unless told otherwise.
Unless it says "but not both", we assume it could be both.

In real life, people tend to hear "either X or Y" as an exclusive choice (you must be one or the other, but not both). But it's all context based.

If it say, "You can't get into Harvard unless you either have a great LSAT score or have a famous parent", you would correctly think that "it's fine to have a great LSAT score and a famous parent"

That's why we wouldn't want to write:
If you got into Harvard and you have a great LSAT score --> you DON'T have a famous parent

And why we would want to write:
if you got into Harvard and DON'T have a great LSAT score --> you must have a famous parent

If you interpret these 'either/or' statements as saying "AT LEAST one of these things must happen", then it would be correct to say
if one of them ISN'T happening, then the other one MUST BE.

whereas it would be incorrect to say
if one of them IS happening, then the other one MUST NOT BE.

Make sense?

[JG350]

Yes, this made complete sense. I think the LSAT vs. real life meanings of either/or confused me. Thanks for the help. Much appreciated