PrepTest 106

[lcid:3520] Prep Test 106 LSAT — Logical Reasoning — S1 Logical reasoning

Question prompt

Psychologist: Some astrologers claim Remaining source text redacted.
Why the credited answer is right

Credited answer: C

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

Astrologers - A person’s horoscope determines their personality
Psychologist - That’s false. Twins are similar, but two people we found born at the same time in Toronto and New York are very different.

Answer Anticipation

This Psychologist attempts to rebut a claim made by Astrologers. They claim that someone’s horoscope completely determines their personality, but the Psychologist claims that this isn’t the case.
In her rebuttal, the Psychologist uses a particular method of reasoning - a counterexample. To show that horoscopes can’t determine personality, she found two people born at the same time (one in Toronto, one in New York) who have very different personalities.
Whenever someone rebuts an argument with a counterexample, we should start by seeing if the counterexample actually counters the initial point. Here, the Psychologist would need two people with the same horoscope but different personalities to rebut the Astrologers. However, she falls short of that by finding two people born at the same time without establishing that that guarantees they have the same horoscope. Maybe time of birth is a part of determining a horoscope, but location is relevant, as well.
Since the argument assumes that the only thing relevant to one’s horoscope is one’s time/date of birth, any answer stating that or ruling out something else that might influence a horoscope will serve as a necessary assumption here.

Answer choices

  1. A
    Astrologers have not subjected Remaining source text redacted.
    Why choice A is not credited
    You can prove someone wrong even if they have subjected their claims to rigorous experimentation, so this answer isn’t a necessary premise.
  2. B
    The personality differences between Remaining source text redacted.
    Why choice B is not credited
    The Psychologist believes that horoscopes don’t determine personalities, so she believes it must be something else. That something else could be cultural differences between locations.
  3. C
    The geographical difference between Remaining source text redacted.
    Why choice C matches the stem
    This answer rules out location as a relevant factor in horoscopes, at least in this case. If the two individuals here lived far enough apart that they did have different horoscopes despite being born at the same time, then they don’t serve as a counterexample to the Astrologers’ point, and the Psychologist’s argument falls apart. This answer is therefore a necessary premise.
  4. D
    Complete birth records for Remaining source text redacted.
    Why choice D is not credited
    The argument only requires birth records to be accurate for the two individuals in question, not that all birth records were kept.
  5. E
    Identical twins have identical Remaining source text redacted.
    Why choice E is not credited
    The identical twins were extraneous to the Psychologist’s argument - if anything, they supported the claims of the Astrologers!

What this tests

Discussion

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