Logical reasoning PrepTest 117 · Section 2 · Question 22

Incorrect. The conclusion here leaves open the possibility that both are wrong (at least one . . . "), so it doesn't have the same flaw as the stimulus where the argument assumed that one of the theories is correct.

Incorrect. This argument doesn't discuss an experiment that it claims will prove one theory and disprove another, ignoring that both can be wrong. Instead, it's flawed because it assumes that David's conclusion is based on relevant premises—it assumes David knows what he's talking about.

Incorrect. This answer doesn't feature two competing theories—it focuses on skill instead of theories, and Jane doesn't have an opinion as to what the specific tree is.

Incorrect. This argument is valid—if someone goes into the forest and counts the trees up, we'll know who is right and who is wrong. The theories are mutually exclusive, but they are also comprehensive—David is either right, in which case Jane is wrong; or Jane is right, in which case David is wrong. Since Jane's theory" is that David is wrong, it's not possible that both theories are wrong, and so this answer isn't parallel to the stimulus.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Flawed Parallel Reasoning

Stimulus Summary:
Dr. G's and Prof. H's theories make mutually exclusive predictions about the upcoming experiment, so the experiment will prove one and disprove the other.

Answer Anticipation:
This argument concludes a prediction about how the results of an experiment will play into support for two separate theories. And those theories have a very particular relationship—what they say about the outcome of the experiment is mutually exclusive.

When two things are mutually exclusive, it means that they can't both be true. So it's absolutely the case that the upcoming experiment can't have results that validate both of the theories. However, that doesn't mean that one is right and the other is wrong. That ignores the possibility that both of the theories are wrong!

The correct answer, therefore, should talk about two things that are mutually exclusive, and then bring up something akin to an experiment that will provide evidence for/against the theories, before concluding that one is right and the other is wrong.

Answer Explanation:
Competing, mutually exclusive theories? Check. Upcoming experiment" that will weigh in on these theories? Check. Concluding that one of the theories will be proven right when it's possible that both are wrong? Check (it could be an oak!). This checks all the boxes, so this is the correct answer.

Key Takeaway:
When dealing with different theories, there are at least two important considerations. First, are they mutually exclusive, or can they both be true at the same time? Second, are they comprehensive and thus represent all potential theories/explanations of a phenomenon, or can they both be wrong with a separate theory being the true explanation?