Inclusive or exclusive 'or'

Michelle H.

How do we tell the difference between an inclusive 'or' (group 3 rules) or an exclusive 'or' (can be negated to mean 'and')?

NotMyName

It will generally come from the context and depend on your translating the true meaning of a given statement. Unfortunately, I'm not aware of any universal rule here.

"I can marry Susan or Beatrice tomorrow". With the reasonable assumption that I am not a polygamist, this is an exclusive OR.

"To score a 180 on the LSAT, you must either study very hard or be very lucky". Can a lucky person who studies very hard score a 180 on the LSAT? Sure. That makes this an inclusive OR.

Does that help?

akistotle

In the real world, if you are asked "what would you like for dessert, ice cream or cake?" I think it means you have to pick one of them, not both. (Well, you can try saying "BOTH!!" and the person who asked you would be like "okay... ")

In the LSAT world, I think the default reading is inclusive (unless it is explicitly stated that it's "not both"). If it says "I'm going to meet A or B", this means "I'm going to meet A or B or both" unless specifically told "but not both." I saw once in Logic Games that says "or both." (A or B or both). But this "or both" is redundant.

But there are times that you have to interpret as exclusive. PT21.S2.Q20 (https://classic.7sage.com/lsat_explanations/lsat-21-section-2-question-20/) says:

A will either take a leave from her company or else she quits

/L --> Q
/Q -->L

But can she do both? I don't think she can take a leave once she quits: Q --> /L; therefore it's Q <-->/L

JustDoIt

@akistotle said:
In the LSAT world, I think the default reading is inclusive (unless it is explicitly stated that it's "not both").

I agree with this. I think that inclusive is the way to go, but like @jkatz1488 mentioned, it really depends on the context.