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part of the sentence after until or without sufficient or necessary?

janenham0510janenham0510 Monthly Member
edited June 23 in Logical Reasoning 31 karma

Hi guys- I am aware from the lessons that until/without is negate sufficient.
But is part of the sentence after until or without necessary condition? (I think this is what Powerscore said)

I am also including an explanation from this website - lsatmax.

We played until it got dark.
/play > Dark (after until)

According to some of JY's explanations, this appears to be the case sometimes but sometimes not.
(or maybe I just got confused... not sure.. haha)
So I get really confused whenever I try to map out sentences including until/without.

Thank you! Much appreciated


  • You Gotta Show MeYou Gotta Show Me Yearly Member
    20 karma

    A good thing to remember is conceptualizing contrapositive of group 3 and group 4 logical indicators for whatever idea you choose to make as SC and NC.

    Your example: /Play -> Dark. Translated back to english: if we did not play, then it was dark.

    Contrapositive: /Dark -> Play. Translated back to english: if it was not dark, then we played.

    As you can see, either works.

  • Matt SorrMatt Sorr Yearly Member
    1020 karma

    I don’t think LSATMax’s explanation is in conflict with JY’s. From what I can tell, they say the same thing, but the methodology is slightly different.

    The difference is that LSATMax recommends always making the part of the sentence before the “unless” or “without” the sufficient condition and making the part of the sentence after those words the necessary condition. So, regardless of how the sentence is structured, you know to negate the first part, make it the sufficient condition, keep the second part as it is, and make it the necessary condition.

    JY, on the other hand, states that you can negate either part of the sentence and make it the sufficient condition. Logically, this is the same as always negating the first part of the sentence. If you choose to negate the second part of the sentence and make it the sufficient condition, then you create the contrapositive of if you negated the first part of the sentence and made it the sufficient condition. As we know, contrapositives are logically equivalent. So, in effect, LSATMax and JY are teaching the same thing. I imagine that LSATMax recommends always negating the same part of the sentence for the sake of simplicity, but it’s logically equivalent to what JY teaches.

  • janenham0510janenham0510 Monthly Member
    31 karma

    Thank you both ! :) this really helps

  • WinningHereWinningHere Monthly Member
    edited June 25 372 karma

    I almost always function with what comes after the until/without as necessary condition and negate the other part. However sometimes it just makes more sense to do it the other way around. We want to remain flexible.

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