#19 - My father likes turnips, but not potatoes, which he

[Administrator]

Complete Question Explanation

Parallel Flaw—SN. The correct answer choice is (B)

The author of this flawed stimulus makes the following conditional argument:

• Some who like turnips do not like potatoes: Turnip-eaters Potato-eaters
  
  Therefore, it is wrong to claim that: Potato-eaters Turnip-eaters

The problem with this argument is that the author only considers one case, which turns out to be irrelevant. He knows one turnip eater who won't eat potatoes. But we are provided with no information regarding those who do eat potatoes, so there is no way to logically draw any conclusion about that group.

The correct answer choice should be guilty of a similar conditional flaw.

Answer choice (A): This attractive distracter may look right at first, but the differences can be seen more clearly when the argumentation is diagrammed:

• This non-paperback is expensive: paperback expensive
  
  Thus it is not true that: paperback expensive

We can see that this argumentation is very different from that found in the stimulus, so this answer choice is incorrect.

Answer choice (B): This is the correct answer choice, representing the following, familiar, flawed argumentation:

• This work has over 75 pages but isn't a novel: more than 75pg novel
  
  Therefore, it is wrong to claim that novel more than 75 pg

As with the stimulus, this choice presumes based on one irrelevant case a presumption about all novels! Since no information is offered regarding books that are novels, this conclusion is invalid and this answer choice is a winner.

Answer choice (C): This answer choice cannot parallel the flawed reasoning of the stimulus, because it is based on valid reasoning: If every ornate building is pre-20th century, then it is valid to conclude that this ornate house is pre-20th century.

Answer choice (D): Like incorrect choice (C) above, this answer cannot be the flawed parallel, as it is based on valid reasoning: in this case, Erica's preferences are sufficient to justify this conclusion. Since she provides an example of a physics-lover who doesn't like pure mathematics, it is valid to conclude that not everyone who likes physics like pure mathematics.

Answer choice (E): This answer choice does not parallel the flaw found in the stimulus; it instead reflects the following Mistaken Reversal:

• Conditional rule: Do own oil changes car fanatic
  
  Neighbor: car fanatic do own oil changes

[netherlands]

Hi there PS,

This problem gave me trouble.

I stared at it first, , then I tried to look at it in an abstract kind of way like question 29 in this same section ( sort of in an A,B,C type way). I got the right answer but it took me forever.

I went back and read your explanation and can now pretty much understand why C, D and E were eliminated. C and D don't commit the stimulus flaw of making a conclusion about a group based of a different group ( the stimulus talks about people who like turnips and dislike potatoes - and then tries to make a conclusive statement about people who like potatoes) ... Additionally, C and D were both valid reasoning and E was a Mistaken Reversal and I could at least understand enough to know that the stimulus wasn't an MR.

But after this A and B are hard to differentiate without diagramming and this is where I couldn't clearly see "conditional" or "causal" diagramming opportunities - so I just tried to randomly diagram and match to an answer choice.

I diagrammed the stimulus as:
A is to Not B ( people who like turnips don't like potatoes)
and
B is to Not A

For A my diagramming was :
Not A is to B
B is to Not A

and for B my diagramming was:
A is to Not B
B is to Not A

That's how I matched B as the correct answer. If this is an okay way and I just need to learn to do it faster than let me know and I'll continue to practice - but if not and this is a crazy way to do it - HELP!

[Steve Stein]

Hey Netherlands,

Good question. It's great that you were able to narrow it down to answer choices A and B. At that point, I might take a quick look for absolute language (all, whoever, e.g.) versus less that absolute (some, many, eg.), because the level of certainty in the argument must be paralleled as well.
For example, if the conclusion were "therefore all Ds are Es," the correct answer choice would have to deal with all or nothing--but it could not say, for example, therefore many Fs are Gs.

In this example, a quick abstract comparison between the conclusions might look something like this:

Stimulus: So it is not true that all As are Bs.
Answer choice A: So it is not true that some As are Bs.
Answer choice B: So it is not true that All As are Bs.

I hope that's helpful--let me know whether this is clear--thanks!

~Steve

[Nikki Siclunov]

Steve is making an excellent point about differentiating between absolute and more tentative language (all vs. some), which is paralleled in B but not in A. That said, let's look at the precise logical construction of this argument and map out the logical flaw in it:

The author questions the truth of the following proposition:

• Like Potatoes Like Turnips

As evidence, he brings up the example of his father, who likes turnips, but not potatoes. This, of course, does not invalidate the initial premise, which provides no assurance that everyone who likes turnips also like potatoes: you can have the necessary condition (liking turnips) without having the sufficient (liking potatoes). The correct way of invalidating that relationship would be to show an instance in which someone who likes potatoes does not like turnips (i.e. the sufficient condition occurs without the necessary condition being there). E.g. answer choice (D).

So, we are looking for an answer choice in which the author erroneously questions the veracity of a conditional statement (A B) by showing an instance whereby the necessary condition B occurs in the absence of the sufficient condition A (i.e. B NOT A). In a way, this flaw in reasoning is predicated upon erroneously inferring a Mistaken Reversal of the initial conditional claim. Answer choice (B) commits an identical flaw in the reasoning, and is therefore correct. By contrast, answer choice (A) does not question the veracity of a conditional relationship and is therefore incorrect. Here's what (A) would sound like, if (A) were to be the correct answer choice:

• This book is not a paperback, but it is expensive. So it is not true that all paperbacks are expensive.

Let me know if this makes sense

Thanks!

[netherlands]

Holy crap. That makes complete and total sense... why did I not see that? I'm going to repeat it back to make sure that I'm understanding it correctly.

Basically, this stimulus is trying to dispute a conditional rule based off of a specific case during which the Mistaken Reversal was false. This is flawed because a conditional rule's validity doesn't require the Mistaken Reversal to be true. So the fact that the Mistaken Reversal was false does not prove that the conditional rule in question is not true.

So the rule:

Likes Potatoes Likes Turnips

Cannot be proven wrong by the ... I guess falsity of its Mistaken Reversal:

Like Turnips Dont Like Potatoes

Based off of that: Answer choice A is wrong immediately because the use of "Some" makes the claim non-absolute and therefore non-conditional.

Answer choice B is correct: The stimulus is disputing the conditional statement that:
If a Novel >75 pages
via a false Mistaken Reversal
Has > 75 pages Not a Novel

- This makes it more clear why the absolute vs non absolute language is so important in this particular question (and between A and B) - it's the difference between whether its an absolute conditional relationship or not.

I also see what you're saying about answer choice D- that specific case does invalidate the conditional rule in question. And C and E are completely different types of arguments.

This kind of worries me though - because I should have seen that and don't understand why I didn't. It's like - I understand the concepts, but I'm not recognizing them each and every time they're used on the test. Or not taking the time to spot and properly attack them.

I'm worried that I have a habit - that I'm realizing I should break- of reading/approaching/attacking some problems based off order of presentation rather than breaking it down and saying "oh that last sentence is a conditional statement they're trying to dispute. Oh, the first sentence is what they use as evidence but is a false mistaken reversal,etc...). I really feel like when I'm under pressure (like when I'm trying to force myself to go at a good pace) its like my brain just abandons all methods I've learned and instead of being discerning while looking at stimuli I just start mowing through them. Does that make sense? I really have to stop that.

Either way, thanks sooooooooo much for explaining that. This problem was super daunting to me less than 24 hours ago, and now makes complete sense.

[bonzobear]

Hello!

I had a hard time with this question because I couldn't figure out the reasoning type and, upon reviewing, was surprised to see this classified as sufficient/necessary. It almost seemed like it was more formal logic than conditional based on the "some" part of the stimulus. The second sentence of stimulus ("whoever likes potatoes..") is very clearly conditional reasoning, but I the first sentence about the father doesn't seem to be so since it's referring to one case/person, therefore "some", therefore more formal logic.

I immediately jumped to answer D since the format of that choice is similar to my abstract (first sentence about one case, second sentence drawing a wider conclusion) but then quickly eliminated that due to the fact that the reasoning there is totally valid. Also quickly eliminated C since that reasoning was correct. Then from there I was just confused about the reasoning type and ended up incorrectly choosing E but didn't like that one any better than A or B!

Anyway, are you able to weigh in on the S/N classification and why it's not classified as FL? Thanks!

[atierney]

Hello!

This is definitely a S/N question, as the question hinges on S/N reasoning, as opposed to FL (which is not implicated here). There is no part of the stimulus that has the word "some," so I'm not sure what you are referring to when you say the "'some' part of the stimulus." This is the stimulus in full: "My father likes turnips, but not potatoes, which he says are tasteless. So it is not true that whoever likes potatoes likes turnips."

In terms of the S/N part: Given, If LP, then LT. Father LT, but not LP, which is used to say that If LP, then LT is incorrect. The conclusion that the conditional is incorrect relies on a mistaken reversal (if LT, then LP), and this is paralleled in answer choice B.

Let me know if you have further questions on this.

[bonzobear]

Hey I was referring to all the "some" diagramming and mentions in the Administrator's post at the beginning of this thread

[Rachael Wilkenfeld]

Hi bonzobear,

This question has elements of both conditional reasoning and formal logic. The main thrust and key concept in the question is conditional reasoning. The question asks you to recognize the flaw in the reasoning which is a problem in the conditional inference. The error is thinking that one (some) instance of the mistaken reversal not working is enough to disprove a conditional. Though it's done with formal logic language (some), it's still a conditional error at it's core.

Hope that helps!

[ashpine17]

so if the stimulus had said whoever likes turnips like potatoes, then wouldn't this have been a valid argument? I need help with A's conclusion; is it P--S--/E or /(P--->E) because it says not true that SOME, so isn't that none?