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Necessary "AND/OR" Confusion. HELP!

LSATChaosLSATChaos Alum Member
in Logical Reasoning 65 karma

https://7sage.com/lesson/advanced-andor-in-necessary-conditions/

I'm having trouble understanding this lesson.
A--> B or C
Why can't "OR" in the necessary mean both? unless otherwise indicated as "not both"
Since its a necessary condition would it not mean that it is necessary for one of them to happen/be triggered but could it not also be the case that B and C happen?

A--> B and C
Similarly for "AND"
I don't understand why AND can split the arrow... if A --> B and C... doesn't this mean that it is necessary for both B AND C to be triggered? Because the contrapositive means if not B or not C then not A... If we say A --> B and A--> C are we saying that one of them could happen without the other and the statement will still be true.. but if this was the case why can't we say or?

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Comments

  • akistotleakistotle Member ⭐ 🍌🍌
    9377 karma

    @LSATChaos said:
    A--> B or C
    Why can't "OR" in the necessary mean both? unless otherwise indicated as "not both"
    Since its a necessary condition would it not mean that it is necessary for one of them to happen/be triggered but could it not also be the case that B and C happen?

    "If Simmi takes a class, then James or Andrew will also take the class."

    S --> J or A

    This does not exclude the possibility of both J and A taking the class. But it doesn't have to be the case that both J and A take the class.

    @LSATChaos said:
    If we say A --> B and A--> C are we saying that one of them could happen without the other and the statement will still be true.. but if this was the case why can't we say or?

    No, I don't think so. A --> B and A --> C mean that A guarantees both B and C.

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