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PT 33 & 36 LG: Conditional Reasoning confusion.

inactiveinactive Alum Member
edited December 2015 in General 12637 karma
Hey 7Sagers! Had a student email me with a question I thought you could help out on. Here it is:

I have this confusion about "A OR B OR BOTH" rule that pertains in DEC 2000 Q.6-12 & DEC 2001 Q.1-6 game that I need you to clarify for me ASAP!

In DEC 2000 Q.6-12 game, rule #2 says: If Jays, Martin, or both are in the forest, then so are harriers.

So you (J.Y.) diagrammed it as:

But in DEC 2001 Q.1-6 game, for the rule # 4 (If the stand carries Watermelons, then it carries figs or tangerines or both), you explicitly warn that we can't diagram it as image because the proper diagramming for that rule is W ----> F or T.

In other words, I can translate A or B -->C as image

but I can't translate A --> B or C as image

even though both conditional reasonings contain the word OR!

So my question is.......does OR function differently when it's put in necessary condition and sufficient condition?


  • StopLawyingStopLawying Alum Member
    821 karma
    Yes, it functions differently. In the sufficient you can split up, but in the necessary you can't. In fact I think there's a lesson on this in the course.
  • tanes256tanes256 Alum Member
    2573 karma
    There is definitely a lesson on this. The diagram as you wrote it would be "and", giving you only one option, if W is in both F and T are in. "Or" gives you three options. If W is in, both can be in or one or the other can be in with W. Best believe there will be a question that tests your knowledge of the "or" rule. If you write the diagram as you did you've probably just screwed up your whole game board, thus potentially screwing up this whole game.
  • LSATislandLSATisland Free Trial Inactive Sage
    1878 karma
    Yes, when OR is in the sufficient condition the diagram reflects that either J or M can trigger H. When OR is in the necessary condition, that same diagram cannot be followed because it would imply that both game pieces must be necessary, i.e. that W triggers F and T, when in fact it is possible that only one (F or T) are triggered.
  • Alex ShortAlex Short Alum Member
    112 karma
    It makes sense to diagram it as JY teaches us. By splitting the necessary condition, it visually indicates by meeting one OR the other sufficient condition, the necessary will be met.

    Likewise, when AND exists in the necessary condition, that can be split with arrows as the OP posted. If AND exists in the sufficient, or if OR exists in the necessary, you must write it out.
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