PT30.S4.Q14 - Joseph and Laura's argument

Stimmy TurnerStimmy Turner Alum Member
edited March 2021 in Logical Reasoning 46 karma

Mistaking sufficiency/necessity flaw

I've been making steady progress on the flaw/descriptive weakening portion of the curriculum however something just isn't clicking with "the oldest trick in the book." The PT30 S4 Q14 wrecked me and it's especially frustrating because I had the flaw anticipated but I just couldn't make sense of what I suspected was the correct answer choice.

I think I need to go back to the drawing board and review the core lessons on sufficiency and necessity because it's not coming very naturally in terms of translating it all back to English especially when denial of the sufficient or necessary happens. I was wondering if anyone had some of those lessons bookmarked because I can't seem to find the ones I remember doing awhile ago and if anyone had any recommendations on dealing with these issues that might've worked for them?

Admin Note: https://7sage.com/lsat_explanations/lsat-30-section-4-question-14/

Comments

  • Sailor Moon LSATSailor Moon LSAT Member ⭐
    200 karma

    Sufficiency/necessity takes a long time to sink in. I would definitely recommend going back to the core lessons. This sounds like overkill but I honestly try to think about everything in real life and how it relates to sufficiency/necessity as a way to practice.

    Something that was helpful for me with sufficiency necessity confusion was a comment I came across in a problem set helping me see that sufficiency/necessity manifests itself in a way that I did not see at first.

    We know that in a logical relationship A-->B, the sufficiency/necessity confusion would be B-->A.

    However, we come across so many arguments that fail the sufficient and conclude negating the necessary (e.g. /A-->/B).

    What I didn't realize was that this is also sufficiency/necessity confusion because if you look above at B-->A, the contrapositive of this is /A-->/B.

    Look at lessons, and then from there I'm sure you can find other ones.
    https://7sage.com/lesson/sufficiency-necessity-what-does-the-arrow-mean/
    https://7sage.com/lesson/the-contrapositive/
    https://7sage.com/lesson/contrapositive-mistakes/

    Try also making a list of problems that have sufficiency/necessity flaws as you come across them, and look at them to see what they have in common.

  • Sailor Moon LSATSailor Moon LSAT Member ⭐
    200 karma

    Also this question is REALLY really hard. I would suggest coming back to it. I came back to it today actually, and only got it right by POE although I knew it was sufficiency/necessity as well afterwards, I just had a hard time seeing what the two variables were. Over time, you will review hard questions and see them in a new light.

  • Stimmy TurnerStimmy Turner Alum Member
    46 karma

    Thank you for the kind words and that's a great way of thinking about it with the contrapositive! I started logging those tough problems like you said and I think you're right about just coming back to it/similar problems and trusting the process that mastery will come.

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