Logical reasoning PrepTest 142 · Section 1 · Question 10

Incorrect. If anything, this answer suggests that Matilde can be confident of its authenticity. Since that rules the first sufficient condition out, and this answer doesn't discuss Matilde's motives in buying the vase, this answer doesn't justify the application of the principle.

Incorrect. Because of the return policy, Matilde can be certain of its authenticity. Additionally, the second half of this answer establishes that it's unlikely she's interested in the vase as an investment opportunity. That doesn't establish that she wants it for its intrinsic qualities, but we certainly can't rule it out. This answer doesn't establish either sufficient condition, so it doesn't justify the application of the principle.

Incorrect. While this answer does establish that Matilde might be interested in the vase as an investment opportunity, it also establishes that she likes its intrinsic qualities. Since the principle is that a person shouldn't want it "just" for its value as an investment, this answer doesn't establish the second sufficient condition. Also, while documentation of age/origin doesn't guarantee authenticity, it also could, so the first sufficient condition isn't definitively established. With neither condition established, this answer can't justify the application.

Incorrect. This answer is silent as to authenticity and strongly suggests Matilde wants this vase for its intrinsic qualities rather than as an investment, so it doesn't trigger either sufficient condition.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen (Principle)

Stimulus Summary:
P: Should buy expensive antique → Confident of authenticity AND Desirable for intrinsic qualities (not just as an investment)

A: Matilde shouldn't buy this expensive antique vase from eBay

Answer Anticipation:
First thing to note is that the principle is about when someone should buy an expensive antique, but the application is that Matilde shouldn't buy a certain antique. The principle sets up a necessary condition for when someone should buy an antique, though, so we need to take the contrapositive to get it to line up with the application:

not Confident of authenticity OR not Desirable for intrinsic qualities → Shouldn't buy

With the contrapositive taken, we can see that there are two individually sufficient conditions to justify the application to Matilde's situation—the correct answer needs to establish either that Matilde can't be certain of the antique's authenticity (it is being sold online, after all, so she can't inspect it); or that she doesn't want it for its intrinsic qualities/she's buying it solely as an investment.

Answer Explanation:
Matilde does like the vase for its intrinsic qualities, so that sufficient condition is ruled out. However, either condition is individually sufficient to justify the conclusion, and this answer establishes that she can't authenticate it, justifying that she shouldn't buy it based on the principle.

Key Takeaway:
In these Strengthen (Principle) application questions, make sure that you get the conditional to line up with the application—it makes everything easy to work with.

When you have a Principle that has two individually sufficient conditions (i.e., an OR sufficient condition), watch out for answers that start by eliminating the possibility that one of the conditions is met! They could still trigger the second condition, so be sure to read all answers in full.