LR Question 14 Explanation
QUESTION TEXT: Investigators have not proved that the forest fire was…
QUESTION TYPE: Flawed Parallel Reasoning
CONCLUSION: The investigators don’t know that the fire was caused by either campers or lighting.
(i.e. The investigators can’t rule out all other causes)
REASONING: The investigators don’t know the fire was caused by campers. They also don’t know whether the fire was caused by lighting.
ANALYSIS: It took me a few readings to see what this argument was saying. I’ll use an analogy.
Suppose three people go into a room, A, B, and C. I hear a scream, open the door, and C is dead. Only A or B could have killed C.
It’s true that I don’t know A killed him, and I don’t that know B killed him. But I do know that one of A or B killed him.
Maybe the investigators ruled out all other causes, apart from fire or lightning. So they know one of the two is the cause, they just don’t know which one.
___________
- CORRECT. If Sada and Brown are the only two candidates, then Kim would have good reason to believe that one of the two will win the election.
- This is a bad argument, but it’s a different flaw. It’s like saying “we have no proof that he got rich by business success, or by magic. So one theory is as likely as the other”.
- We can’t say most are from out of town, since it could mostly be non-engineers who are from away. But this is not the same error as the stimulus. The stimulus didn’t even use ‘most’ statements.
- You can’t ever combine two some statements. While this is an error, it’s different from the error in the stimulus. The stimulus didn’t use any some statements.
- This is a different error. It’s like saying “Obama can win, and Romney can win, therefore they can both win together”. Obviously, only one person can be elected president.
More Resources for Flawed Parallel Reasoning Questions
- Conditional Reasoning Article: Learn about conditional statements.
- LR Diagrams Guide: Learn how to draw LR diagrams.
- Flaw drills: Practice identifying flaws.
- Intro Course lesson: This intro course lesson covers Flawed Parallel Reasoning questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers flawed parallel reasoning questions.
Graeme, I don’t (still after reading your analogy) understand why the stimulus exhibits a flawed pattern of reasoning…
This is a tricky question because the flaw in the argument is unusual (especially on the LSAT) and the wording of the stimulus makes it even more difficult to discern. The gist of the flaw is this: just because we can’t prove that lightning caused the fire or that campers caused the fire separately, doesn’t mean we can’t narrow down the total possible causes of the fire to two. Maybe the investigators were able to definitively rule out every other possible cause besides lightning and campers. So, they could be certain that it was either campers or lightning that started the fire, and still be unable to prove each possibility separately.
That’s why (A) is correct–just because we can’t prove that Kim will win the election, or that Brown will the election, doesn’t mean that they’re not the only possible candidates. Maybe either Sada or Brown must win because there are no other candidates, so the conclusion doesn’t necessarily follow from the premises.
Look at it this way:
Premise #1: I have no reason to believe that Clinton will win the 2016 elections.
Premise #2: I have no reason to believe that Trump will win the 2016 elections.
Conclusion: I have no reason to believe that either Clinton or Trump will win the elections.
The flaw is to assume that there are more candidates to vote for, or overlook the possibility that there are only two candidates to choose from.
Yep, that’s correct. To elaborate a bit: the flaw is not taking into account that the only possible outcome is that one of these two candidates must win the election.
For A, When it says “So Kim has no reason to believe that either Sada or Brown will win the election.” Doesn’t that imply that Kim believes that someone else will win (as opposed to either Sada/Brown)
The statement you quoted is the conclusion. It can’t prove anything. The statement does show the author BELIEVED it must be the case that someone else could win.
But the point is that the author could be WRONG. Kim might not have a belief about who will win, but she might still believe that one of them will win.
Got this right. But not very international-friendly of the LSAT because other countries often have more than two candidates….and the question doesn’t specify that there are only two.
I think you meant to add this to another question? This question’s about forest fires.