LR Question 9 Explanation
QUESTION TEXT: We know that if life ever existed on the Moon…
QUESTION TYPE: Parallel Reasoning
CONCLUSION: Life has never existed on the moon.
REASONING: If life had existed on the moon, there would be evidence. We haven’t found evidence so far.
ANALYSIS: Absence of evidence is not evidence of absence. Something can exist even if we haven’t found it yet. That’s all there is to this argument. Often the error is quite simple.
___________
- The stimulus had absence of evidence, and used it to prove evidence of absence. We looked for evidence, and couldn’t find any.
This argument has a different structure. First, it just says “we don’t know”. We don’t know if people tried to find out whether the general was a traitor.
Second, the stimulus has a clear conditional link between life and evidence of life. If there were life, there’d be evidence.
This argument has shown no conditional link between being a spy and being a traitor. - This doesn’t match the structure. The conclusion is “unlikely”, whereas the stimulus said there has “never” been life on the moon.
Further, in the stimulus people actually looked for evidence of life. Whereas this loser couldn’t even be bothered to open his fridge to check for mayo. - This is a terrible argument, but it doesn’t mirror the absence of evidence flaw.
The flaw here is that the argument gave no evidence about what concerns voters. Unless they care about crime, Hendricks doesn’t have a chance. The argument said what Hendricks wants, but not what voters want. - This is a bad argument, but the error is different. Here, finding signs of rodents is a necessary condition. The argument incorrectly takes it to be a sufficient condition.
- CORRECT. This matches the absence of evidence error. The author has shown that we haven’t found troop movements or a transfer of weapons. But that doesn’t mean those things don’t exist.
More Resources for Parallel Reasoning Questions
- Conditional Reasoning Article: Learn about conditional statements.
- LR Diagrams Guide: Learn how to draw LR diagrams.
- Intro Course lesson: This intro course lesson covers Parallel Reasoning questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers parallel reasoning questions.
When I was taking this question, I got tripped up on the fact that in answer E there were two conditional outcomes instead of one. In other words:
Prompt Argument: If life ever existed on the moon, there would be signs of life there. Translated: If A, then there would be B. Since there is no indication of B, therefore no A.
Answer E: If the army is planning an attack, there would be troop movement OR a weapon transfer. If A, then there would be B OR C. Since there is no indication of B or C, therefore no A.
Is this a difference that shouldn’t be considered?
Either way, admittedly, I should’ve realized B was wrong — in my haste I misread the second clause as “the refrigerator IS empty” instead of “the refrigerator is almost empty” — doh! I also failed to notice the “unlikely.” sigh.
My question is this though: let’s just say, hypothetically, that answer B did say “the refrigerator is empty” and “we don’t have any mayonnaise” instead of “almost” and “unlikely” — would those changes make it a better answer than E, considering the difference i mentioned above w/ the multiple vs singular conditions the element A would lead to?
I ask just because the fact that E isn’t a fully parallel argument either is throwing me through a loop.
On parallel reasoning questions you’re looking for the argument that is most similar. Typically LSAC will make arguments that are exactly similar, but it’s fine if an argument diverges on a small point. Graeme actually asked LSAC about this and they confirmed it in great detail, you can read more here: https://lsathacks.com/lsac-responses/
So, in E “troop movements…or a transfer of weapons” should be considered as a certain element (so together, it would be B in if A B). So it is a fully parallel argument, and in terms of finality (“never been life on moon” and “no indication of troop/weapon” are both pretty definite).
As for your hypothetical, if it said “If we have mayonnaise, it would be in the fridge. But the fridge is empty, so we don’t have mayo”, that would be more correct.
Thank you for the thorough response. I appreciate that you took the time to respond to each element of the question I posed — so often in online comment sections/forums people will answer a similar, simpler (dumber) question that wasn’t what was actually asked, so I really appreciate that your response perfectly addressed my question.
… ya’know upon further reflection, I probably ought not be too surprised that the website with a crack team of LSAT aficionados would also happen to be the one place online where forum responses perfectly address complex questions posted by users, lol.
I still really appreciate it, though.
Glad that we can help!