LR Question 21 Explanation
QUESTION TEXT: Although the first humans came to Australia 56,000…
QUESTION TYPE: Flawed Parallel Reasoning
CONCLUSION: Human diseases couldn’t have killed the animals in Australia.
REASONING: No single human disease could have killed the animals in Australia.
ANALYSIS: This argument sounds good, but it slightly switches terms: the conclusion talks about human diseases, plural. But the evidence is about what a single disease can do.
Maybe 7 different human diseases would have been enough to kill the 55 species that died when humans arrived in Australia 56,000 years ago.
Effectively, this argument makes a part-to-whole flaw: it assumes that because a single disease can’t do it, then a group of disease also can’t do it. The right answer, though superficially different, also makes a part-to-whole flaw.
You might ask: how can I spot tiny stuff like “disease vs. diseases”? Well, use your intuition. When I read the conclusion, I thought “of course we could kill animals with diseases, we have a lot of diseases”. I didn’t assume I was right, but having that thought let me look carefully at the argument and I noticed the switch in terms.
Listen to your intuition. It isn’t certainly right, but it can give you clues. (Past a certain point, LSAT prep is mostly about training your intuition to be better)
___________
- This actually isn’t a terrible argument. It makes us realize we need more information before blaming interest rates.
- CORRECT. This makes the same error in a different form. In the stimulus, the error was assuming that because no single disease could do it, then all diseases combined also couldn’t do it.
In this argument, neither person alone can fix the house, but it’s possible that both people combined could fix the house.
This certainly is not a precisely parallel argument, but it parallels the central flaw, which is the main criteria for choosing an answer. - You might have picked this because you thought “Well, no single restaurant can satisfy them, but what if all restaurants combined can satisfy them.”
That doesn’t work because of….common sense. The argument says that Lena, Jen and Mark want to eat together. The three of them can’t eat together at separate restaurants, so this is a good argument. - This is a bad argument: we only know most recent art is not great. Some recent art could still be great.
But this utterly fails to parallel the argument, which made a part to whole flaw. - This is a good argument. It correctly shows that the influenza vaccine sometimes reduces symptoms even when it doesn’t prevent the disease.
(Note that if there are symptoms to alleviate, then the vaccine didn’t prevent the disease. That’s how we know the “some” is not part of the group which has the disease prevented.)
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.
Okay. I got it wrong first round but I’m studying, too. So, here:
I chew it down and asked myself “wtf”, and like, okay “it doesn’t consider the rest”. Bingo. Let’s look for that in the answer
(B) is right because
It doesn’t consider the rest [of the things left to fix in the apartment, yet already whining that they can’t fix everything without outside help]
Related back to the CORE, in a sense that:
It’s (probably) not human diseases (feel the “all” in there?) that causes the mass exctinction because one disease couldn’t cause it.
It doesn’t consider the rest of the human-borne diseases… (assuming there’s just so many species – then JUMP to the conclusion that ALL of them could have not been the cause).
…assumes because they can’y only fix some things each, that since a door and a window are broken, jumps to the conclusion that they can’t fix ALL.
Feel me?
Exactly. Your analysis is correct. The stimulus says that just because a single human-borne disease can’t wipe out all the species, none of the “new diseases” (plural, more than one) together could’ve done it. Similarly, like you said, just because two people can only fix one thing each doesn’t mean they need to call for outside help to get everything done. They can each fix one thing, just how each virus can take out a few species.
I chose A because it had the closest structure to the stimulus. When solving parallel flaw questions is that something to consider? Or, am I supposed to be internalizing the flaw and then searching the answer choices for that same structure? My reasoning for eliminating B was that it did not have the “probably” mentioned in the stimulus. Thank you.
This is a good question, because it highlights a significant difference between parallel reasoning and parallel flaw questions. In parallel reasoning questions, it’s very important to internalize the structure of the stimulus and the level of qualification of the conclusion (e.g. if it uses words like probably, unlikely, sometimes, etc.). You can eliminate answers on the basis of structure for parallel reasoning questions.
In parallel flaw questions, the structure and the level of qualification might not match–as we see in this question–but the flaw might be the same, rendering it the correct answer choice. That’s why it’s essential to not eliminate answers exclusively on the basis of having a structure that doesn’t match that of the stimulus. We’re just looking for a parallel flaw.
For answer C, the answer choice mentions restaurants “in the immediate vicinity”. I assumed they could venture out further to find more restaurants, and I chose c because I expected lsac to make that assumption
Making that assumption would actually suggest the argument is flawed because it doesn’t consider an important alternative, i.e. that they can venture outside the immediate vicinity of the theater to find something that satisfies them all.
1. There are no restaurants that satisfy Lena, Jen, and Mark in the immediate vicinity of the theater
Therefore, they will probably go straight home after the show.
So, even bringing in that outside assumption, the argument flaw still does not match the part-to-whole flaw in our stimulus.
Now I understand!!!! Thanks. The argument in the stimuli has a flaw of “part to whole”. C is also a flawed argument but the flaw is probably “false dilemma”?
Yes, C is a variant of false dilemma, and also lack of common sense. Things that might happen after the show:
They might head outside the immediate area for dinner
They might split into two groups
One person might decide to go to a restaurant they don’t like in order to hang out
Note: This is an old comment but I wanted to clarify the point.