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Neither nor is a biconditional?

JoeyPotatoJoeyPotato Member
in Logic Games 18 karma
PT16-S1-G1, trying to setup the rules with conditionals and having a bit of an issue trying to figure out why Rule 3 " Neither S nor W can be added to the same class as Y" is a biconditional for S-Y and S-W instead of just a single conditional. Biconditionals are either/or/but not both and I cannot for the the life of me back that out from this conditional statement. Any help would be greatly appreciated. I can work out S-->/Y based on group 4 negate necessary but that's all........
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  • runiggyrunruniggyrun Alum Inactive Sage Inactive ⭐
    2481 karma
    I think you might be confusing a biconditonal relationship with a premise/contrapositive relationship. The example you give is not a biconditional relationship.
    A biconditional would be S<-->/Y, which would suggest that not having Y in a class means you necessarily have S. That's not true, as you have three classes, and there will necessarily be one with neither S nor Y.
    The contrapositive of the original rule (S-->/Y) can be written as Y-->/S (negate and reverse), and that accurately represents the relationship. If you have S, then you can't have Y, and if you have Y than you can't have S (because they are "forever apart").
    The same goes for the S/W relationship.
    For grouping games (as opposed to in/out games) I find it helpful to notate these sorts of rules as a vertical box with S and Y in it and a slash through, to visually represent that you can't have both in the same group.
  • JoeyPotatoJoeyPotato Member
    18 karma
    https://7sage.com/lsat_explanations/lsat-16-section-1-game-1/

    In this video around the 1:46 mark it appears JY is representing the relationship as a biconditional. I agree with your single conditional translation. The way I came up with S-->/Y is group 4, negate necessary, and the or in the sufficient can be split up to make S-->/Y and W-->/Y.
  • runiggyrunruniggyrun Alum Inactive Sage Inactive ⭐
    2481 karma
    @JoeyPotato - there's a note in pink below the video that clarifies that the biconditional notation in the video is a mistake - I didn't notice that until now.
    Nice catch!
  • JoeyPotatoJoeyPotato Member
    18 karma
    The nice catch was by you.... Pointing out that note in pink that I missed. I have spent the last 2 days trying to figure this out!!!! Thanks for your help.
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