Logical reasoning PrepTest 145 · Section 2 · Question 21

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen (Principle)

Stimulus Summary:
P: not Criticize a certain behavior in yourself AND not Vow to stop → Shouldn't criticize that behavior in others

A: Shimada doesn't vow to stop being tardy → Shouldn't criticize McFeney for tardiness

Answer Anticipation:
The conclusion of the Application matches up with the necessary condition of the principle as stated, so there's no justification needed there.

However, the sufficient condition doesn't match up. And noticing why requires us to take a step back and figure out how our diagram has an AND sufficient condition despite using the word OR in the language.

Let's think about a similar condition—Let's say there's a burger that costs $5, but there are also coupons for a free one. We could say: If you don't have $5 or a free coupon, you can't get a burger. Does that mean that not having $5 means you can't get the burger? Nope—you could have a coupon. And we could flip that around. So this would, similar to the stimulus, diagram as not $5 AND not Coupon → not Burger.

What's going on here is that the initial "not" in these phrases is grammatically being used to apply to the entire phrase—If one does not (criticize OR vow to stop). The negation, then, applies to each term—including the linkage, and a negated OR is an AND.

With that out of the way, let's hop back to see how the Application doesn't meet the sufficient condition. While it has been established that Shimada meets one of the joint sufficient conditions (not vowing to stop), it doesn't establish that he meets the other one. Therefore, to justify the application of the principle, it must be established that Shimada also doesn't criticize himself for his tardiness.

Answer Explanation:
The relevant portion of this answer choice is the last clause—Shimada doesn't criticize his own tardiness. With the other information in the Application, this answer justifies the conclusion that he shouldn't criticize someone else's tardiness.

Key Takeaway:
Be careful with AND/OR conditions that feature a leading negation. It's easy to apply that negation to only some of the parts of the condition, when it should apply to everything—including the AND/OR linkage.

Incorrect. Even if Shimada is almost never tardy, that means he's tardy sometimes. This answer doesn't establish, however, that he fails to criticize himself for it, so it doesn't justify the application of the principle.

Incorrect. This answer doesn't address whether Shimada ever criticizes himself for his tardiness, which is the missing piece of information to allow the principle to be applied.

Incorrect. By criticizing himself for tardiness, Shimada guarantees that the principle doesn't apply to him and thus the application can't be justified.

Incorrect. This answer doesn't address Shimada's criticism of his own irregular tardiness, so it doesn't justify the application of the principle.