PrepTest 111

[lcid:3542] Prep Test 111 LSAT — Logical Reasoning — S3 Logical reasoning

Question prompt

Teacher to a student: Remaining source text redacted.
Why the credited answer is right

Credited answer: D

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Argument

Valid or Flawed

Flawed

Question Type

Strengthen with Necessary Premise Questions

Stimulus Summary

Principle 1 - It’s bad to break a promise
Principle 2 - We implicitly promise others that we’re telling them the truth
Specific situation - The student promised Jeanne he’d tell the teacher she’s home sick, but the student knows she’s not
Judgment - The student shouldn’t tell the teacher Jeanne is home sick

Answer Anticipation

Wow - the teacher is really laying it on thick, here! This is an interesting question, in that we get several principles and a judgment, making this similar to a Principle question. However, it’s instead a Necessary Premise question, so let’s unpack it.
The Teacher starts out by establishing two principles, both of which tell us something is wrong to do. The first one tells us that breaking a promise is wrong. The second builds on that, as it’s still talking about breaking a promise - however, here, it brings up an implicit promise we all make to tell the truth. That’s a promise that would be broken with a lie.
From here, the teacher gets into the specifics of the given situation. While the language is all couched in conditionals (“even if…”, “if you know…”), but let’s assume that those are true for a second to talk through the situation.
First, the student promised Jeanne that he would tell the teacher she was sick. So not doing so would break that promise. However, the teacher concludes that the student shouldn’t say that - thus breaking his promise - if he knows Jeanne isn’t sick. Why? The rationale behind that is, if it’s a lie, then saying it breaks the implicit promise not to lie.
So the teacher has highlighted that the student is in a pickle - breaking a promise to Jeanne would be bad, but so would breaking the implicit promise to the teacher not to lie. Since the teacher sides with not lying, he’s assuming that breaking that implicit premise is worse than breaking the explicit promise the student made to Jeanne. Let’s find an answer that aligns with that.

Answer choices

  1. A
    Most people always tell Remaining source text redacted.
    Why choice A is not credited
    The teacher’s argument relies only on lying being the breaking of an implicit promise. It doesn’t rely on how frequently that implicit promise is broken.
  2. B
    It is sometimes better Remaining source text redacted.
    Why choice B is not credited
    There’s no discussion of what’s in Jeanne’s best interests. Maybe not getting in trouble for skipping school is in her best interests; maybe getting in trouble and thus possibly being put back on the straight and narrow is. This answer is thus out of scope.
  3. C
    Breaking a promise leads Remaining source text redacted.
    Why choice C is not credited
    First, consequences are out of scope here. However, even if you assumed that you should avoid worse consequences when possible, this answer would establish that the student should not break the promise to Jeanne and instead tell a lie, since that would lead to better consequences, thus undermining the teacher’s argument.
  4. D
    Some implicit promises are Remaining source text redacted.
    Why choice D matches the stem
    The teacher establishes that telling the truth is an implicit promise. The student made an explicit promise to Jeanne. In concluding that the student should keep the implicit promise and break the explicit one, the teacher is assuming that there are times when an implicit promise should be kept and an explicit one broken, as this answer states. If no implicit promise is worse to break than an explicit one, then the student shouldn’t break the promise to Jeanne, completely undermining the teacher’s conclusion. This answer is therefore a necessary premise.
  5. E
    One should never break Remaining source text redacted.
    Why choice E is not credited
    If one should never break a promise, then the student shouldn’t break the promise to Jeanne or the implicit promise not to lie. That leads to a logical contradiction/impossible situation.

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