Q14 - Investigators have not proved that the forest fi

[ohthatpatrick]

Question Type:
Match the Flaw

Stimulus Breakdown:
Conclusion: Investigators haven't proved that blaze was caused by campers or lightning.
Evidence: They haven't proved it was started by campers, and they haven't proved that it was started by lightning.

Answer Anticipation:
Hmmm, sounds pretty valid, right? Yet we know there MUST be a flaw. How could it be that you've failed to prove X and failed to prove Y but still proved "X or Y"? I guess we can imagine a scenario where the cops KNOW the killer was Bob or Dave, even though they still can't prove which one of the two actually did the killing. Structurally speaking, we want something like P1: Haven't proven X. P2: Haven't proven Y. Conc: Haven't proven "X or Y".

Correct Answer:
A

Answer Choice Analysis:
(A) Sure this seems to work. No reason for X, no reason for Y, thus no reason for "X or Y". In a close call election, you might have no reason to believe the Republican will win and no reason to believe the Democrat will win, but you still have reason to believe "the Republican or the Democrat will win".

(B) Conclusion is not an "either/or" statement, so let's not bother reading the whole thing.

(C) Conclusion is not an "either/or" statement, so let's not bother reading the whole thing.

(D) Conclusion is not an "either/or" statement, so let's not bother reading the whole thing.

(E) Conclusion is not an "either/or" statement, so let's not bother reading the whole thing.

Takeaway/Pattern: That ended up being a very easy, quick Matching question. It was simple to represent the argument in terms of "not X, not Y, thus not 'X or Y'." and surprisingly only one conclusion even had that form.

#officialexplanation

[marcus.v.p.]

Quick question. What is the flaw? The stimulus seems logical to me.

[mselvaratnam]

I would love to know this as well. I got it wrong because the closest matching answer didn't seem to have a flaw.

My theory is that while the two facts in the premise are true on their own, their validity may come into question once the other statement comes into play.

i.e. Maybe they haven't proved that the fire was started by campers, but perhaps once they prove it wasn't started by lightning, that gives them the proof they need to say it was the campers that caused it. Having the second bit of knowledge falsifies the first.

Same thing could be true in A, where having no reason to believe Sada will win might be enough reason to believe that Brown will win.


In any case, I'm hoping it's something more obvious, because while I made that distinction during the PT, I dismissed it as a vague hunch.

[fmuirhea]

You're on the right track. I don't know if this flaw has a formal name, but I'll try to explain my reasoning below.

Just because you haven't proved A or B independently does not mean you haven't definitively narrowed it down to the two. I'll try to illustrate with an analogy: the Ravens and 49s are playing in the Super Bowl. Analysts haven't proved that the Ravens will win, nor have they proved that the 49s will win. Therefore, they haven't proved that the Ravens or 49s will win. (Sure they have - they're the only options!)

(A) matches up - even if we can't make a good case for either candidate, it's possible they're the only two on offer.

(B) tries to equate the probability of each theory, but the stimulus does not discuss likelihood.

(C) is a flawed interpretation of quantifiers, but not the pattern we're looking to match here. (most A are B + most A are C = some A are B and C)

(D) is another flawed interpretation of quantifiers. (some A are B + some A are C = nothing!)

(E) shows evidence for two competing theories and then concludes that both could be true at once. I don't know if we're meant to assume (as we might in the real world) that only one person could possibly drive a car at once (and thus dismiss the conclusion for being slightly absurd), but either way, this pattern of reasoning doesn't match up with the stimulus.

stimulus: can't prove (A), can't prove (B), therefore can't prove (A) or (B)
(E): could be (A), could be (B), therefore could be (A) & (B)

[daijob]

It feels like questions these days become trickier and cannot sort out into traditional types

[muriella]

Got this question correct but strictly on structural basis....but I still have no idea what the actual flaw was. Could a Manhattan geek enlighten please on the nature of this flaw? As another poster suggests, this one seems unrecognizable from the regular "types" we have seen in the books and in class.

Thanks in advance...

[christine.defenbaugh]

Interesting question, muriella!

I think an earlier poster nailed it when they said the flaw was essentially "Just because you haven't proved A or B independently does not mean you haven't definitively narrowed it down to the two." Is this a 'classic flaw' - meh, not really. But it's still a flaw!

While the LSAT does love to ask about a variety of classic logical fallacies (causation/correlation, sufficient/necessary, part/whole, etc), there are infinite possible flaws out there that don't fit into these neatly defined, classic categories. That doesn't necessarily mean those flaws are a lot harder though!

Consider this argument:
Pizza has cheese. Therefore, it's delicious!

What's the flaw? The author is assuming that cheese makes things delicious. Is that a classic flaw? Surely not! And yet, it's relatively simple to identify. On a fundamental level, arguments are flawed because they assume things, and assumptions don't always fit into perfectly defined categories. This is why lists of common flaw types (or argument structures) are absolutely useful, as long as you don't start thinking those lists are the sum total of the flaws/arguments in the world!

I know that at first glance, this conclusion looks like it is just restating the two pieces of evidence! (If that were the case, it wouldn’t be much of an LSAT conclusion, nor would it be flawed!) But consider for a moment that you have two terrible cats. You leave them all day in your apartment, with no one else there, and the doors and windows securely locked. When you return home you find your favorite vase in pieces on the floor with sticky kitty paw prints all over the pieces and the surrounding floor. Can you prove it was Mungojerrie? No. Can you prove it was Rumpleteazer? No. But you surely can prove it was one or the other of them (or perhaps both)! You just don’t know which.

What do you think?

[muriella]

Thanks Christine! Thanks for helping me caste aside my tunnel vision when it comes to identifying flaws. Just because there was no official "type" for this flaw in this q, didn't make it any less so of one.

Thanks again for the detailed explanation.

[erikwoodward10]

Interesting question, muriella!

I think an earlier poster nailed it when they said the flaw was essentially "Just because you haven't proved A or B independently does not mean you haven't definitively narrowed it down to the two." Is this a 'classic flaw' - meh, not really. But it's still a flaw!

While the LSAT does love to ask about a variety of classic logical fallacies (causation/correlation, sufficient/necessary, part/whole, etc), there are infinite possible flaws out there that don't fit into these neatly defined, classic categories. That doesn't necessarily mean those flaws are a lot harder though!

Consider this argument:
Pizza has cheese. Therefore, it's delicious!

What's the flaw? The author is assuming that cheese makes things delicious. Is that a classic flaw? Surely not! And yet, it's relatively simple to identify. On a fundamental level, arguments are flawed because they assume things, and assumptions don't always fit into perfectly defined categories. This is why lists of common flaw types (or argument structures) are absolutely useful, as long as you don't start thinking those lists are the sum total of the flaws/arguments in the world!

I know that at first glance, this conclusion looks like it is just restating the two pieces of evidence! (If that were the case, it wouldn’t be much of an LSAT conclusion, nor would it be flawed!) But consider for a moment that you have two terrible cats. You leave them all day in your apartment, with no one else there, and the doors and windows securely locked. When you return home you find your favorite vase in pieces on the floor with sticky kitty paw prints all over the pieces and the surrounding floor. Can you prove it was Mungojerrie? No. Can you prove it was Rumpleteazer? No. But you surely can prove it was one or the other of them (or perhaps both)! You just don’t know which.

What do you think?

I don't see how your analogy applies. The conclusion of the stimulus isn't saying that that the investigators cannot or will never prove that the fire was caused by campers or lightening, it is saying that so far they haven't. That seems logical. Likewise, A seems perfectly logical to me too. You have no reason to believe A, and you have no reason to believe B. So you have no reason to believe A or B.

I still don't understand the flaw in this question. I started out focusing on the shift form "started by" in the premise to "caused by" in the conclusion, but this was difficult to match (partly because it's not the right flaw).

[YT]

I don't see how your analogy applies. The conclusion of the stimulus isn't saying that that the investigators cannot or will never prove that the fire was caused by campers or lightening, it is saying that so far they haven't. That seems logical. Likewise, A seems perfectly logical to me too. You have no reason to believe A, and you have no reason to believe B. So you have no reason to believe A or B.

I still don't understand the flaw in this question. I started out focusing on the shift form "started by" in the premise to "caused by" in the conclusion, but this was difficult to match (partly because it's not the right flaw).

The investigators could still have ruled out all the possible causes except lightning and campers, but they could be not able to prove which one of the two is the cause.

Similarly, Kim could know that all other candidates except those two (B and S) are not going to win the election, but he could be not able to say definitely which one is going to win. Maybe because Kim knows that all other candidates are not going to be approved by a commission which is required to approve candidacies.

[christian.zeigler]

I think the language here might have cleared up the logic, if the language had been more formal.

Instead of how it was phrased, how about: "So, the investigators have not proved that the blazed was caused by NEITHER campers NOR lightning."

The way it was written, it could be read as: "So, the investigators have not proved that the blazed was caused by campers and they have not proved that the blazed was caused by lightning."

This is an English issue. In the latter case, there is no logical flaw; in the former, the flaw is much more obvious.

Hope this helps someone. This was a failing on the part of the LSAC, one of many; there should not be multiple ways to read something for this kind of question.

[ohthatpatrick]

The substituted version you provided actually has a double negative, so it's not saying what you want it to. You'd want it to say "they haven't proven that it's EITHER campers OR lightning".

I agree that the provided conclusion can be interpreted different ways, given the freedom Parallelism provides us in dividing up the sentence.

"They haven't proven that the fire was caused by campers or lightning" could be interpreted as

"They haven't proven that the fire was caused by campers or lightning"
or
"They haven't proven that the fire was caused by campers or by lightning."

But given the question stem, which asks us to model Flawed reasoning, it would seem weird for us to use the logically valid interpretation.