PrepTest 101

[lcid:3501] Prep Test 101 LSAT — Logical Reasoning — S2 Logical reasoning

Question prompt

Copernicus's astronomical system is 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

Illustration Questions / Principle Questions

Stimulus Summary

Ptolemy: The stars revolve around the earth
Copernicus: The earth rotates on an axis
At the time, evidence supported both theories, but the latter was simpler, so it was and is a superior theory.

Answer Anticipation

Principle (Strengthen) questions generally present a judgment in the conclusion based on details in the premises, and the correct answer connects those details to the judgment.
Here, the judgment is a relative one - Copernicus’s theory was and is superior to Ptolemy’s. Since this conclusion is a comparison (“superior to”), we should focus on the details in the premises that establish points of comparison.
And in those premises, there are two. The first is that both theories were “equally consistent” with the evidence available at the time they were proposed. Since the conclusion is about a difference (one being superior to the other), this likely isn’t going to connect to it! The second is that Copernicus’s theory is “simpler” than Ptolemy’s. Since this is a difference between them, the argument must be relying on it to justify the conclusion. Let’s find a principle that establishes that for two theories that both fit the evidence, the simpler one is the better one.

Answer choices

  1. A
    Simplicity should be the Remaining source text redacted.
    Why choice A is not credited
    This is a tempting trap answer! However, this answer doesn’t fit with the argument in the stimulus. There, the simplicity was relevant only because the two theories each fit the observational data. If simplicity were the sole deciding factor, then all scientific explanations would be, “A wizard did it!”

  2. B
    If one theory is Remaining source text redacted.
    Why choice B is not credited
    There’s no discussion of either theory likely being true or false, so this answer is out of scope.

  3. C
    If all observational evidence Remaining source text redacted.
    Why choice C is not credited
    While the two theories were consistent with all observational evidence, there’s no discussion of their relative intuitiveness. Rather, it discusses the relative simplicity, which is different. Something can be complex but intuitive, or simple but unintuitive!

  4. D
    Other things being equal, Remaining source text redacted.
    Why choice D matches the stem
    This answer discusses one theory being “inferior” to another, which is the flipside of one being “superior” to another. Since this can justify the conclusion, we should see if it matches with the details. And it does. Other things - here, the theories being consistent with the evidence - were equal between the two theories. The author then uses the simplicity of Copernicus’s to conclude that it’s the superior theory. Unlike answer (A), this allows for other factors to be important if they’re different. This answer thus lines up with the argument and justifies the conclusion, so this is the correct answer.

  5. E
    Other things being equal, Remaining source text redacted.
    Why choice E is not credited
    The argument discusses which theory is superior, not scientifically important, so this answer is out of scope.

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