LSAT 149 | Section 4 | Logical Reasoning: Q25

LR Question 25 Explanation

QUESTION TEXT: The police department has two suspects for the…

QUESTION TYPE: Flawed Parallel Reasoning

CONCLUSION: Forster is the burglar.

REASONING: The burglar could be Schaeffer or Forster. Schaeffer has an ironclad alibi.

ANALYSIS: This argument forgets that Schaeffer and Forster aren’t the only possible suspects. There might be other potential thieves that the police don’t currently suspect.

So we can’t say Schaeffer is the burglar unless we rule out all other possible suspects.

The structure is: There was one robber, two suspects exist, one is ruled out, the argument incorrectly concludes the remaining suspect is guilty without ruling out the possibility of other suspects.

___________

1. This isn’t strong enough. First, we only have “good reason to believe” the primate house will be built. That’s not as strong as Schaeffer’s “ironclad” alibi.
   Second, there’s only one robber, so Schaeffer and Forster can’t both be guilty. But this argument hasn’t said why the zoo can’t both build a primate house and refurbish the polar bear exhibit.
2. This is an incorrect negation. It’s a different flaw.
   Statement: Lineup ➞ Reasonable
   Incorrect Negation: Lineup ➞ Reasonable
3. This answer says what Iano should do. That’s a moral principle. The stimulus was a question of fact: Forster is the robber. On the LSAT, fact and moral principle are completely different. 
4. CORRECT. This matches the error. There are two options that are, in fact, exclusive: the company can’t move to both Evansville and Rivertown. But, like the stimulus, this answer forgets there are other options. The company might decide not to move, or it might move to some other place (Smithsburg?). The argument should have excluded all other options apart from Evansville or Rivertown.
5. This is a good argument. There are only two candidates, so one of them does have to be elected. In the stimulus, the author didn’t say the two suspects were the only two suspects.