PrepTest 112

[lcid:3547] Prep Test 112 LSAT — Logical Reasoning — S4 Logical reasoning

Question prompt

Joseph: My encyclopedia says Remaining source text redacted.
Why the credited answer is right

Credited answer: B

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

Argument or Facts

Argument/Argument

Valid or Flawed

Flawed/Flawed

Question Type

Argument Structure Questions

Stimulus Summary

J: Fermat’s theorem hasn’t been proven since his death, so it probably can’t be proven, and thus Fermat’s claims to have proven it are wrong or a lie.
L: Someone recently proved the theorem, so it’s provable, and so Fermat did prove it.

Answer Anticipation

Note that the question stem is asking us to describe the role of a statement in Joseph’s argument, so we can ignore Laura’s for the purposes of this question.
Looking at Joseph’s argument, it starts with a historical fact, so we have background information (though Fermat’s claim to have proven the theory isn’t pure background - it’s more an opposing point). It then pivots to the statement in question, and a key word was left out of it in the question stem - it starts with “Probably.” Words that denote certainty such as this one tend to show up in conclusions, as it’s the Author qualifying how certain they are (here, over 50%). That the statement in question is a conclusion is backed up by it having a “since” after it, which introduces a premise in support of a conclusion in the same sentence.
However, then we run into a wrinkle - the final sentence has a “Therefore,” showing that it is also a conclusion. So we’ll need to determine which conclusion is the main point, and which is the intermediate conclusion.
Looking at them, the theorem likely being impossible to prove supports Joseph’s claim that the person claiming to have proved it is wrong or lying, not the other way around. So that makes the statement in question the intermediate conclusion - let’s find an answer reflecting that.

Answer choices

  1. A
    an assumption for which Remaining source text redacted.
    Why choice A is not credited
    Assumptions are unstated, so since the statement in question shows up in the stimulus, this answer can’t be correct.
  2. B
    a subsidiary conclusion on Remaining source text redacted.
    Why choice B matches the stem
    This answer matches our anticipation. The failure of anyone else to prove the theorem supports the view that it probably can’t be solved, which supports the conclusion that Fermat - who claimed to have proven it - was lying or wrong.
  3. C
    a potential objection that Remaining source text redacted.
    Why choice C is not credited
    Joseph believes that the theorem probably can’t be solved, so this isn’t an objection he’s attempting to address.
  4. D
    the principal claim that Remaining source text redacted.
    Why choice D is not credited
    Joseph’s argument is meant to refute Fermat’s claim that he proved the theorem, not that the theorem is likely impossible to solve.
  5. E
    background information that neither Remaining source text redacted.
    Why choice E is not credited
    If anything is background, it’s the opening line that provides the history of the theorem.

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