#21 - Although the first humans came to Australia 56,000

[emilysnoddon]

I had a lot of trouble with this question. Based on logic I was totally sold on answer choice B, however, the fact that answer choice B definitively says "the two of us will be unable to repair our apartment" while the stimulus says "probably" caused me to rule this answer choice out. I ended up choosing answer choice C based on lack of an alternative. I thought I was taught by PowerScore that in parallel reasoning questions the correct answer choice must reflect the strength of the conclusion in the stimulus. I am very confused about this question. Can someone please clarify?

[Clay Cooper]

Hi emily,

Thanks for your question.

You are correct that the respective degrees of certainty in the stimulus and the correct answer choice are different; the stimulus, as you point out, says 'probably,' while the conclusion of the correct answer is stated with certainty.

You are also correct that, usually, degree of certainty in the conclusion is very important in parallel reasoning and parallel flaw questions. However, there are exceptions to this general rule, because in every LR question our task is to pick the best answer. (Note how in this question stem we are asked to find the 'most parallel' argument).

In other words, answer choice B is the only argument amongst the answer choices that commits the error of composition that we see in the stimulus argument. Therefore, even though its degree of certainty is different, it is definitely still the most parallel: the other choices are either valid reasoning or make different errors.

I hope that helps.

[JSLSAT]

Hi PowerScore,

Would you mind going a bit more in-depth on how to break down the stimulus and then answers B and C? Had a very tough time with this.

Thanks so much

[Adam Tyson]

I'll try, JS! As Clay mentioned in his prior post, the error here is one of composition, also know as a part-to-whole flaw. The author assumes that since no one single disease could be responsible for all the extinctions, then the sum total of all the new diseases could not have been to blame. He has overlooked the possibility that one disease might account for some extinctions while another disease accounts for other extinctions, and so on.

The same flaw occurs in answer B here - the author assumes that since no one person under consideration (the two roomies) is able, on their own, to repair both the window and the door, then they cannot, in combination, fix them both. Perhaps one can do the window and the other the door?

Answer choice C has no such part-to-whole flaw. There is a flaw here - perhaps they are willing to go to a restaurant that they don't like? Maybe they will head outside the immediate vicinity of the movie theater? Maybe instead of dinner they will hit a club, or go hang out in a park, or hop a freight train and ride the rails a while, hobo-style? - but it's not the same type of flaw. I would say that it's a false dilemma - the author assumes that because one choice they might make is unlikely, they have only one alternative (going home). Sure, he hedges his bets by saying they will "probably" do that, but even so, there is no real evidence that that is probable, not without more info.

I hope that helps!

[JSLSAT]

Yes - very, very helpful. I definitely got stuck on that "other flaw" in C, but looking at it as a false dilemma is definitely helpful. Thank you!

[1month2go]

Upon reading the stimulus I thought the flaw was a causal reasoning error. The author assumed that there could be only 1 cause - 1 disease - that caused the mass extinction when in reality there could have been multiple, so I looked for an answer that similarly neglected to consider other or multiple possibilities for a specific effect, but that didn't work out so well. Is it totally unreasonable for me to think there was an error of causation here? Reading over the stimulus again I guess I see how the author made the mistake of assuming that just because one disease could not have caused it that no disease could is a part to whole flaw, but it didn't immediately jump out at me.

Hopefully you can shed some light.

Thanks!

[Alex Bodaken]

1month2go,

Thanks for the question! No, I think your thought process is entirely reasonable - that's actually what jumped out to me at first, as well. But of course, once we see that none of the answer choices adequately mirror this flaw (that the author jumps from multiple diseases to one disease), it's time to go back and look for another flaw, and in this case the one that is mirrored is error of composition.

Hope that helps!
Alex

[zsg2@cornell.edu]

Is is not possible to look at the stimulus as posing a false dilemma (i.e. that author is assuming either one disease caused the mass extinction or it was not the diseases at all, when in reality it could have been a combination of diseases that caused the mass extinction)? In this light, C) would look even stronger given the additional parallel structure of the conclusion where C's conclusion goes further than the stimulus. Thanks.

[Rachael Wilkenfeld]

Hi zsg,

It's similar to a false dilemma in that it fails to consider something. However the more specific flaw here is the way the author confuses part-to- whole. It's that just because one disease alone couldn't do something, doesn't mean that all the diseases together couldn't do something. That's different than saying because one didn't do something, nothing could have. It's not that there was potentially a single other virus that had the impact. It's that the group of viruses as a whole could do it.

Hope that helps!

[sqmusgrave]

Hello! I've found the practice you guys recommend for parallel Q types of making the flaw/reasoning abstract really helpful. Could someone please tell me how to formulate the stimulus' flaw in abstract terms?

I can see the flaw by thinking "well maybe different human diseases affected different populations, and it's the combination of multiple disease strains that caused the mass extinction. Or perhaps human disease caused a few key species to go extinct, and like a domino affect this disrupted the food chain causing mass extinction." This was enough to hone in on B, but it was all very intuitive and fuzzy because I couldn't describe the flaw in more generally applicable terms. It would be really helpful if you guys could show me what an abstract version of this flaw might look like.
Thanks!