Q23 - Physics professor: Some scientists claim

[aileenann]

Oh boy, this is a tough problem. The first thing I'd recommend is that anyone who has access to Atlas recordings or who is taking an Atlas course put this question off, because we cover it in one of the last class sessions as an extra tough assumption question

That said, I'll also put a brief explanation up for those who feel they mostly have a handle on this one.

The first thing, as always with an assumption question, is you should figure out the core. Here it's that:

I saw some ball lightning that didn't look the way it did if plasma caused it -> therefore plasma is never a cause of ball lightning.

Folks, that bolded never is not there by accident. That's what points to a "problem" with this argument that needs to be fixed. Saying I saw one thing therefore I can effectively eliminate forever and always an alternative explanation is pretty extreme. I must be assuming that seeing one is seeing enough.

That matches up with the correct answer - (E). (I'll get to the incorrect answers, but since this one is tough, it's important to first focus on why the right answer is right.) This answer is oddly easy to read compared to the argument, and tells us that all ball lightning has the same cause. Well think about it, if all ball lightning has the same cause, then I really don't need to see more than one. And I don't need to see more than one, then neither does the professor to eliminate the super-heated plasma alternative.

I hope that helps for those of you who might be scratching your head about this one If not, (a) don't worry and (b) somewhat unconventional, but I premise this works, consider replacing "super heatd plasma" by "cake" and making similarly silly but fair substitutions for the other scientific jargon. That may help it to make more sense, and you'll preserve the logical structure.

Now to the wrong answers.

(A) is out of scope. We only care about ball lightning. We don't care about other kinds of lightning.

(B) is also out of scope. We have no reason to mistrust the professor, so who cares how many other people saw the lightning.

(C) is the *opposite* of what the professor is assuming. If (C) were true, the professor's argument would be totally flawed because he would be drawing a conclusion on the basis of a single observation even knowing that it could have multiple explanations and causes.

(D) is redundant. We know this from the premises in the argument already. A premise is not an assumption, so you don't want to pick an answer choice as an assumption that tells you something you know already from the argument.

I hope this helps. Hit me up with questions and comments if you have any.

[debbie.d.park]

I am having a hard time trying to sort out the logic stem of this question. Would appreciate your help!

[giladedelman]

I am having a hard time trying to sort out the logic stem of this question. Would appreciate your help!

[giladedelman]

Hi Debbie,

Thanks for the question. Do you mean you're having trouble understanding the argument itself? Let's take a closer look at it.

The professor starts by introduce a claim: superheated plasma in which electrical resistance fails (hereafter to be referred to as cake) is a factor in ball lightning.

If cake really did cause ball lightning, the professor continues, the lightning would emit intense light and float in the air. But since the ball lightning he has observed didn't do those things, it must be true, according to him, that cake never causes ball lightning.


(One way to think about the logic of this argument, in addition to Aileen's awesome explanation, is that it's kind of like saying this:

"People say smoking cigarettes can cause cancer. But the cases of cancer I've seen have all been in people who didn't smoke. Therefore, smoking cigarettes never causes lung cancer.")

So, Debbie, does that help you understand this one any better? Please let me know if you're still unclear about it.

[debbie.d.park]

Yes, that clears up all the confusion. Thanks so much!

[ManhattanPrepLSAT1]

Thanks for the question!

Let's start by identifying the conclusion and the supporting evidence.

Conclusion
Superheated plasma with failed electrical resistance is never a factor in causing ball lightning.

Evidence
1. If superheated plasma with failed electrical resistance was a factor in causing ball lightning, then such lightning would emit intense light and rise in the air.
2. The instances of ball lightning that the professor observed did not emit intense light and did not rise in the air.

We can establish from this evidence that the instances of ball lightning that the professor observed were not caused by superheated plasma. But that's not strong enough to guarantee that "super heated plasma... is never a factor in causing ball lightning." We need an answer choice that will bridge the gap from the instances the professor observed to all ball lightning. Answer choice (E) does this by saying that all types of ball lightning have the same cause. If that's true, then if some ball lightning is not caused by superheated plasma, then no ball lightning is caused by superheated plasma!

(A) is out scope. We are not concerned with other types of lightning other than ball lightning.
(B) supports the evidence, but does not bridge the gap between the evidence and the conclusion.
(C) undermines the argument but introducing the possibility that what caused the ball lightning the professor observed was different than what causes other instances of ball lightning.
(D) is out of scope as it discusses gaslike substances in general.

Takeaway: Some of the hardest Sufficient Assumption questions have a structure like this: One thing is observed, and a conclusion is drawn about all such things. In order to guarantee that the observation represents all possibilities, we can establish an "all or nothing" scenario. Since the observation tells us it isn't "nothing," we're able to conclude that it's "all."

Does that help clear this one up? Let me know if you still need a bit more help with it!
#officialexplanation

[tamwaiman]

Please help to find out my blind spot. Many thanks!

ERF: electrical resistance fails
BL: ball lightning
IL: intense light

some scientists: ERF -> BL -> IL
Physics professor: BL -> ~IL, therefore, ERF is never the cause.

So, there are two types of BLs (IL & ~IL), if (E), all types have the same cause, then the only one same cause would be ERF and hence the professor is wrong.


After reading the stimulus I was looking for a answer like "ERF is not the cause unless IL", how sadly no such answer and it took me five minutes at least.

[ManhattanPrepLSAT1]

Please help to find out my blind spot. Many thanks!

ERF: electrical resistance fails
BL: ball lightning
IL: intense light

some scientists: ERF -> BL -> IL
Physics professor: BL -> ~IL, therefore, ERF is never the cause.

So, there are two types of BLs (IL & ~IL), if (E), all types have the same cause, then the only one same cause would be ERF and hence the professor is wrong.

Keep in mind that the professor never claims that all ball lightning does not have intense light - which is what your notation above would suggest.

Also I think you'll run into trouble with your notation of the second sentence. You might want to try...

SHP ---> IL + RI
BL some ~IL + ~RI

(SHP = superheated plasma causes ball lightning, IL = intense light, RI = rises in the air)

from these we can infer

BL some ~SHP (some ball lightning is not caused by superheated plasma)

The argument concludes that

BL ---> ~SHP

But how do go from "some ball lightning is not caused be superheated plasma" to "no ball lightning is caused by superheated plasma?"

We make it an all or nothing game - as answer choice (E) accomplishes. Does that answer your question?

[irini101]

Hi Geeks, this question reminds me of the conditional reasoning + causality pattern formula I have read in other posts in this forum and also arouses another question in when to apply the formula:

the stimulus can be diagrammed as:

(electr resis --> ball light) --> intense light + rise in air
~intense light/ ~rise in air --> (elect resis -|-> ball light)

in this question, the contrapositive is considered incorrect because there could be more than one cause besides electr resis for ball light.

It fits the following pattern of conditional reasoning + causality:

(A--> B) --> C
~C --> (A-|-> B)

but this pattern is considered correct in other posts in the forum, which conflicts the diagram of ball light above. So my question is: this pattern is correct under the condition that we suppose there is only one cause of B (A)? If there's more than one cause of B (as the situation for ball light), then the formula does not fit right?

Thanks in advance!

[nflamel69]

So does this question deal with unrepresentative sampling? When I read the question I immediately thought what if the ones that the professor saw wasn't representative, maybe he saw some ball lightning that are caused by other factors, since the first sentence said the SHP is a factor. so for the conclusion to be right, then we have to assume that every single ball lightning have to have that factor. shit, then we have a cause and effect problem... eh.. I thought I got this one down, now I'm confused, can any Geeks clarify this?

[austindyoung]

The Physics Professor states that "the instances of ball lighting I observed.." and then goes on to explain it and then goes on (via the an "incorrect" contrapositive) to categorically deny SHP causes Ball Lighting.

The professor doesn't state that the ball lighting he observed actually came from SHP. Maybe the ball lighting he observed was actually coming from a radioactive cake on YouTube.

My question is: Are we supposed to assume that the phenomenon (bad BL) he observed actually came from SHP? Because the stimulus doesn't state that he does- and it seems that this would be a Necessary Assumption (and yes, I know this is a Sufficient Assumption Q).

I know this is a little different than what we are talking about- but I have seen the same stims used for a variety of different question types.

Thanks

EDIT: I think I answered my question, with the help of The Sherm. So, he writes

We can establish from this evidence that the instances of ball lightning that the professor observed were not caused by superheated plasma.

We know this because: the professor observes ball lighting. He concludes that SHP is never a factor in causing that ball lighting. Well- then he couldn't have been using superheated plasma for whatever composed of his observation because it would have produced the low intensity and horizontal ball lighting.

I guess this was confusing for me because even though he is talking about two types of ball lighting, his conclusion is about all ball lighting.

[austindyoung]

the stimulus can be diagrammed as:

(electr resis --> ball light) --> intense light + rise in air
~intense light/ ~rise in air --> (elect resis -|-> ball light)

in this question, the contrapositive is considered incorrect because there could be more than one cause besides electr resis for ball light.

It fits the following pattern of conditional reasoning + causality:

(A--> B) --> C
~C --> (A-|-> B)

but this pattern is considered correct in other posts in the forum, which conflicts the diagram of ball light above. So my question is: this pattern is correct under the condition that we suppose there is only one cause of B (A)? If there's more than one cause of B (as the situation for ball light), then the formula does not fit right?

Thanks in advance!

It's not an incorrect contrapositive- I think that's counter-intuitive... The problem is that the argument doesn't take the contrapositive. It goes a step further and is incorrect. Matt Sherman explains it:

SHP ---> IL + RI
BL some ~IL + ~RI

(SHP = superheated plasma causes ball lightning, IL = intense light, RI = rises in the air)

from these we can infer

BL some ~SHP (some ball lightning is not caused by superheated plasma)

The argument concludes that

BL ---> ~SHP

But how do go from "some ball lightning is not caused be superheated plasma" to "no ball lightning is caused by superheated plasma?"

We make it an all or nothing game - as answer choice (E) accomplishes. Does that answer your question?

[taaron]

Is another related (but perhaps more obvious) assumption that all instances of ball lighting have the same properties? I was looking for this in the answer choices, though I see how E works in its place.

Thank you!

[Crogati]

I'm excited to say I have reached a point in my studies where the logic in this argument is clear to me, so I thought I'd share the knowledge with others. Here is a distilled version:

(E) is correct because if all types of ball lightening have the same cause then intense light and rising in the air is absolutely necessary for ball lightening (take the contrapositive of 2nd sentence and remember the "and" becomes an "or"). Thus, the absense of either factor is sufficient to ensure the physics professor did not see ball lightening. But for the absense of these factors to NEVER be a factor in ball lightening then the presence of these factors must always be necessary for ball lightening.

[erikwoodward10]

Still struggling with this question. If I understand correctly, we have to take the professor at his word and use the evidence he presents.

He presents a claim that some scientists believe in the first sentence (some scientists claim that SHP where ER fails is a factor in causing BL).

The second sentence provides a premise that would be true, given that the first sentence is true (If this were so, BL would emit IL and rise).

Then he denies observing the necessary effects that would be required if the first sentence was true (I did not see IL or rise).

Finally he concludes that given this evidence, the first sentence is actually incorrect (SHP never causes BL).

If we just take the professor at his word, it seems to me that his argument is already airtight. He sets required conditions (IL and R) which must be present if SHP causes BL. He denies these conditions. Thus, he dienes the validity of the first sentence.

This seems like a clear contrapositive.

cause/effect
(SHP --> BL) --> IL +R

~IL + ~R --> (SHP --I--> BL)

So to me answer choice E seems irrelevant, it doesn't matter if ball lightning has 1 or 1,000,000 causes, according to this argument SHP simply does not cause BL. Ever.

I've read over the posts in this thread a few times, but I can't seem to catch my error. Any insight would be greatly appreciated!

EDIT: Reading through the above posts AGAIN, I'm realizing that it may be useful to state that I'm using PowerScore methods to try and solve this problem (basic CR), but not what PowerScore calls "formal logic" ("some" statements). Are these necessary to solving this problem correctly? It seems that another post above is using conditional some arrows.