Logical reasoning PrepTest 106 · Section 2 · Question 18

Question prompt

Dobson: Some historians claim Remaining source text redacted.
Why the credited answer is right

Credited answer: A

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

Errors in Reasoning Questions

Stimulus Summary

Historians: Two stones in Stonehenge line up with the sun at a special time, so the people who built it knew about astronomy. Dobson: There are a lot of stones, so there was a good chance they’d point at something important. Therefore, the builders didn’t know about astronomy.

Answer Anticipation

As with all Errors in Reasoning questions, we should be on the lookout for elements that are associated with specific flaws. Here, even though the stimulus wasn’t broken out into two speakers, we did get an argument and a rebuttal, so we broke those out in our Summary. When dealing with a rebuttal, there are a few common flaws that can appear. The rebuttal might miss the mark on the original point, but here, Dobson talks about celestially significant events and brings up reason to doubt the argument the Historians actually make, so there’s no Straw Man or Red Herring flaw. Second, it might use a key term in a different sense, but “celestially significant” seems to mean some important thing in the sky/space, so there’s no Ambiguous Word Usage here. Third, it might attack the people who made the opposing point, but Dobson doesn’t call the Historians names. Fourth, when the conclusion is the polar opposite of the opposing point, there’s a chance that there’s an Absence of Evidence flaw. Generally, the way this flaw works with a rebuttal is that the author will highlight a legitimate problem with the opposing point, but then instead of saying that the opposing conclusion might be false, it says that it is false. But highlighting a flaw in an argument only proves the possibility the conclusion is wrong - after all, there might be another argument that establishes it as true. And that’s what happens here. Dobson points out that the evidence used by the Historians to reach their conclusion doesn’t prove that the ancient builders had astronomical knowledge. From that, he concludes that they didn’t - when really, all he proved is that it’s not certain they did. That’s an Absence of Evidence flaw, so let’s find an answer reflecting that.

Answer choices

  1. A
    The failure of cited Remaining source text redacted.
    Why choice A matches the stem
    This is the generic Absence of Evidence flaw answer, so it’s correct. The Historians cite the evidence of the stones pointing to the sun during the equinox as proof of their conclusion. Dobson shows that that evidence fails to establish the conclusion, and she treats that as sufficient to prove that the conclusion is false.
  2. B
    Dobson's conclusion logically contradicts Remaining source text redacted.
    Why choice B is not credited
    Dobson’s conclusion is that the builders didn’t have knowledge of celestial events. To contradict the premises, Dobson would have to have presented evidence they did have such knowledge. Instead, she showed that a correlation between the stones and celestial events was a statistically likely coincidence - something that doesn’t contradict the conclusion.
  3. C
    Statements that absolutely establish Remaining source text redacted.
    Why choice C is not credited
    This answer would describe an argument where Dobson proved a conclusion, but then reached a weaker one. Not only is that not a flaw, it’s also not what happened here. If anything, Dobson proved something might be false and then concluded it is false - the opposite of what this answer describes.
  4. D
    Something that is merely Remaining source text redacted.
    Why choice D is not credited
    While it might be impossible to ever know whether the builders knew astronomy since we can’t exactly ask them, it’s still a matter of fact whether they did or not, not a matter of opinion.
  5. E
    Dobson's drawing the conclusion Remaining source text redacted.
    Why choice E is not credited
    As we noted in our Anticipation, Dobson doesn’t shift the meaning of a key term from the Historians’ argument. The only term that really could shift here is “celestial event/celestially significant,” but there’s no sign Dobson is excluding the sun during the spring equinox as celestially significant.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A Credited 60%
  2. B 16%
  3. C 4%
  4. D 17%
  5. E 3%

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Discussion

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