PrepTest 127

[lcid:3604] Prep Test 127 LSAT — Logical Reasoning — S1 Logical reasoning

Question prompt

Essayist: Common sense, which Remaining source text redacted.
Why the credited answer is right

Credited answer: E

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

Must Be True Questions

Stimulus Summary

Common sense - A collection of time-tested, useful theories
When a new, more useful theory is found, it replaces the old theory, but slowly, so there are always some obsolete theories.

Answer Anticipation

This Must be True stimulus is one of those that describes a general phenomenon and will likely have an answer that either abstracts from it, or deals in the details. So it’s important that we understand it.
It starts by defining common sense as a set of time-tested, useful theories. From there, it describes how it evolves - when a new, useful theory is found, it replaces an old one, albeit slowly.
The stimulus also ends with a very strong statement - common sense “always” contains some obsolete theories. Such a strong statement is usually related to the correct answer, so we should keep our eyes out for something dealing with that final clause.

Answer choices

  1. A
    At least some new Remaining source text redacted.
    Why choice A is not credited
    The stimulus doesn’t discuss theories that won’t be absorbed into common sense, so while the weak nature of this answer (“At least some”) is a plus, it ends up out of scope. These theories might eventually prove to be more useful than current theories.
  2. B
    Of the useful theories Remaining source text redacted.
    Why choice B is not credited
    The new theories proved to be more useful than the old theories they replaced, but not more useful than the still present old theories. There’s no basis for this comparison to be drawn, so we can rule this answer out.
  3. C
    The frequency with which Remaining source text redacted.
    Why choice C is not credited
    There’s no reason given for the slow absorption of new theories, so we can’t infer one, as this answer choice tries to do (“the frequency...prevents”).
  4. D
    Each theory within the Remaining source text redacted.
    Why choice D is not credited
    There’s no indication that every theory included in common sense will eventually be replaced - it could be that there are some timeless theories in there!
  5. E
    At least some theories Remaining source text redacted.
    Why choice E matches the stem
    New, more useful theories “gradually” replace the old theories, and the slowness means that there are “always” obsolete - i.e., in the process of being replaced - theories. Therefore, these old, obsolete theories that are still a part of common sense are less useful than the new ones that are still in the gradual process of being absorbed. We have generic examples of what this answer choice says, which is enough to support an answer about “[a]t least some” theories.

What this tests

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