Logical reasoning PrepTest 109 · Section 3 · Question 21

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
Some economists: Our home countries aren't influenced by external factors

Author: Economies are always open systems (e.g., international trade), so Economists have to consider external factors if their economies are to prosper.

Answer Anticipation:
The vast majority of the difficulty in this question is focusing on the logic instead of the tangential material. And by tangential material, we mean the analogy/comparison. How can we tell that's tangential?

If the argument were relying on that analogy to prove its point, two things would be true. First, there would be a clear indication that the author was using it as a premise—something like, "Since," as an introductory word. Second, the argument wouldn't present direct evidence—here, that economies are always open systems.

Additionally, it's very hard to make an argument based on an analogy airtight, as a Strengthen with Sufficient Premise tasks us with doing. The analogy has to be established as being similar in all relevant features, and those features need to be established as sufficient to justify the conclusion in both cases. As such, it's exceedingly unlikely that the correct answer in this question will deal with the analogy.

With that stripped away, the argument is a lot more straightforward—external factors affect an economy, and so economists need to consider these factors when getting an economy to prosper. The correct answer should connect these statements—e.g., Economists need to consider any factor that influences an economy when figuring out how to get that economy to prosper.

Answer Explanation:
Rephrasing this to make it easier to analyze—If every significant influence on an economy hasn't been analyzed, then a national economy can't prosper. Or, a nation's economy prospering requires all significant influences to be analyzed. This justifies the conclusion that external factors must be analyzed for the nations's economy to prosper, and so this is the correct answer.

Key Takeaway:
The LSAT is not beyond throwing extraneous information into a stimulus. In fact, sometimes it's done to misdirect you away from what would otherwise be a relatively straightforward argument!

Incorrect. As we discussed in our Anticipation, the analogy is tangential to the argument. That said, if anything, the argument would be justified if the analogy were airtight, not "weakly" analogous.

Incorrect. This answer is comparative—"less accurate"—which can't justify the non—comparative conclusion that deals in a requirement for an economy to prosper.

Incorrect. International trade is offered as a single example of an external factor that influences an economy. Even if it's the "primary" factor in prices and wages that doesn't establish that such factors need to be analyzed to allow a country's economy to prosper as it's possible that the causes of prices and wages don't need to be understood to get that outcome.

Incorrect. First, this answer more or less repeats the opening line. Second, what economists are doing doesn't necessarily speak to what they must do in order to get an economy to thrive.