Logical reasoning PrepTest 139 · Section 4 · Question 21

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
Skiff's book published this year → Nguyen promises to urge dean to promote SkiffNguyen will keep her promise
Nguyen urges dean to promote Skiff → Skiff promoted
Therefore - Skiff's book is as good as he claims → Skiff promoted

Answer Anticipation:
Oh boy. This conditional logic-based argument has a lot of implicit premises and connections that we'll have to straighten out before we can find the gap. That said, we can start from a position of strength. The conclusion has two parts—the sufficient condition isn't mentioned or inherently related to any idea in the premises; the necessary condition is. This tells us first that we should look for an answer that connects a premise and that sufficient condition, and second that we should see how the premises relate to (and establish) the necessary condition.

So starting from that necessary condition, what does guarantee that Skiff will be promoted? Well, that's guaranteed if Nguyen urges the dean to promote him. What would guarantee that will happen? There's no conditional that guarantees she will urge the dean to promote Skiff, just that she has promised to do so. But! The stimulus also establishes that she will keep that promise, so we can treat that necessary condition as saying she will urge the dean to prompt Skiff if his book is published this year.

So the stimulus establishes that if Skiff's book is published this year, then Skiff will be promoted—and we're out of premises. In order to justify the conclusion, therefore, we need to connect the sufficient condition of the conclusion to the sufficient condition of the chain in the premises:

Skiff's book is as good as he claims → Skiff's book published this year

Note the direction here—since the premise chain builds to the necessary condition of the conclusion, we need to build from the conclusion's sufficient condition to that chain.

Answer Explanation:
This answer connects the sufficient condition of the conclusion to the sufficient condition of the chain from the premises that leads to the necessary condition of the conclusion. In other words, it adds the missing link between the sufficient and necessary conditions of the conclusion.

Key Takeaway:
This Strengthen with Conditional Logic question features two patterns that can make this question type much easier. First, it has a new term/concept in the conclusion that therefore must be addressed in the correct answer—that by itself gets us down to (A) and (D). Second, it has a trap answer that's a reversal/negation of the correct answer. To avoid this trap, we need an answer that mirrors the structure of the conclusion, as far as what terms show up in the sufficient and necessary conditions.

Incorrect. The conclusion has the promotion as the necessary condition, and this answer establishing a necessary condition for the promotion is therefore a reversal.

Incorrect. Nguyen's belief as to the quality of the book is out of scope. She's promised to urge a promotion if it's published this year, and her beliefs as to its quality aren't linked to whether or not it's published or whether or not she'll keep that promise.

Incorrect. This answer connects the concepts that need to be connected, so it should be considered. It diagrams as: not Important and well-written as Skiff claims → not Published. Two issues here. First, this answer is about the book being published, not published this year. That said, if it isn't published, then it won't be published this year. Second, if we take the contrapositive to get this to line up with the conclusion, we get: Published → Important and well-written as Skiff claims. That's a reversal of the connection we're looking for, since at this point there's no premise that builds from the book being as important and well-written as claimed, and thus this answer can't justify the conclusion.

Incorrect. This answer establishes a necessary condition for the promotion, and that promotion is the necessary condition of the conclusion, so this answer is a reversal.