Q12 - People who say that Dooney County

[abcde]

Hello,

I'm having a trouble with this question. I do understand why (B) is the answer, but I don't quite understand why (C) is wrong.

Would anyone please help me?
Thank you.

[KakaJaja]

Hi Kang, here's my thought:

The argument reasons:
Premise1: Flat --> ~Erosion -->~Terraces
Premise2: Terraces
Conclusion: ~Flat

So we know that if there is no soil erosion, the ppl there don't need to build terraces for purpose of preventing soil erosion. However, they may still build it for other purposes, for example, they build terraces to grow crops that needs much water. Therefore, we need assumption in B to tell us that the terraces in Dooney are exactly for soil erosion.

For C, assume there are three kinds of terraces in the world, X, Y and Z. Dooney county built the X. Yes, we know that the same kind of terraces X is used for soil erosion in Springfield county, but in Dooney county, the terraces X is used to grow crops that need water. If so, the argument still can't hold. In short, having been shown to prevent soil erosion somewhere else can't guarantee us that terraces here are for the same purpose in Dooney.

Hope it helps!

[abcde]

"Having been shown" can't guarantee that it is used in different places for the same purpose!

Thank you very much!

[agersh144]

I still don't understand this question can someone please break done the core of the argument MLSAT style and then break down each answer choice and explain where A and D specifically do astray? Thanks!

[tommywallach]

Hey Agersh,

Happy to help!

Conclusion: Dooney County isn't flat.
Premises:
1) Farms in Dooney County have terraces.
2) Flat land doesn't suffer soil erosion by water
3) Farmers don't need to plant terraces to prevent erosion

The problem here is that farmers might build terraces for some other reason other than the prevent erosion (for aesthetic value, maybe).

(A) The argument doesn't depend on this assumption. Even if soil could be eroded by wind, that wouldn't explain the terraces, which are said to only protect against erosion by water.

(B) CORRECT. This is the point I made. We need to know the terraces were built to prevent soil erosion (rather than for aesthetic value, as I suggested). If they were, then it follows the land isn't flat, because otherwise the terraces wouldn't be needed for that purpose.

(C) We already knew this from the passage!

(D) We don't need to know flat land doesn't have soil erosion, but that flat land doesn't have soil erosion by water (which the passage told us already).

(E) This would not help explain why the terraces are there.

Hope that helps!

-t

[agersh144]

Thanks Tommy, great explanation!

[woof90]

I am unsure about the explanation given for AC (A).

The stimulus does not seem to tell us at all whether terraces are built to prevent erosion by water specifically, so I don't understand how A is ruled out. It only says that farmers whose land is flat do not build terraces to prevent erosion. So I don't see anything preventing those farmers building terraces to prevent soil erosion by wind, for example, in which case the author has made an assumption that soil erosion must be by water only.

Help!

[einuoa]

I guess this is a really late reply, but I'm stuck on this question while working out my LSATs too. The way I thought about it is that say for example the question did depend on the assumption of A, that the only cause of soil erosion is water, that means that farmers whose land is flat do not suffer from soil erosion at all, therefore they would really have no need for terraces to prevent erosion. But, since there are farms in Dooney County dotted with terraces, the terraces must be to prevent soil erosion, and so Dooney County must not be flat because they have terraces. That would rely on another assumption that the terraces are used only to prevent soil erosion in Dooney County, and not for anything else. Based on the text, I can't assume that Dooney County uses terraces only to prevent erosion just because it could be used to prevent erosion. That's like saying that drinking orange juice is used to prevent colds, but it doesn't mean that drinking orange juice is ONLY used to prevent colds, since people drink orange juice for its tastiness too.

Choice B on the other hand addresses that assumption that we were trying to make even when we chose A, that the terraces were built to prevent soil erosion. If there are terraces built just to prevent soil erosion, then there must be soil erosion in Dooney County. The second premise
farmers whose land is flat --> do not build terraces to prevent erosion
(I'm not sure if I'm diagramming that with the arrows correctly)
and if you take the contrapositive, since there are terraces built to prevent erosion, that means the farmer's land isn't flat, because otherwise why would he need terraces?

I hope that helps!

[michaelwcarper]

Hey Agersh,

Happy to help!

Conclusion: Dooney County isn't flat.
Premises:
1) Farms in Dooney County have terraces.
2) Flat land doesn't suffer soil erosion by water
3) Farmers don't need to plant terraces to prevent erosion

The problem here is that farmers might build terraces for some other reason other than the prevent erosion (for aesthetic value, maybe).

(A) The argument doesn't depend on this assumption. Even if soil could be eroded by wind, that wouldn't explain the terraces, which are said to only protect against erosion by water.

(B) CORRECT. This is the point I made. We need to know the terraces were built to prevent soil erosion (rather than for aesthetic value, as I suggested). If they were, then it follows the land isn't flat, because otherwise the terraces wouldn't be needed for that purpose.

(C) We already knew this from the passage!

(D) We don't need to know flat land doesn't have soil erosion, but that flat land doesn't have soil erosion by water (which the passage told us already).

(E) This would not help explain why the terraces are there.

Hope that helps!

-t

Regarding A...where is it specified that the terraces only protect against erosion from water? I'm having trouble seeing why it's not a necessary assumption.

[ohthatpatrick]

I think the bold excerpt from Tommy's last post was a mistake. He didn't really mean that the paragraph ever told us that terraces are ONLY meant to protect against erosion by water.

I can see why people are tempted by (A).

It wouldn't have anything to do with the Main Conclusion, but it seems germane to how the author reaches his subsidiary conclusion.

Prem:
on flat land, soil erosion by water isn't a problem.
(Consequently)
Subsidiary Conc:
on flat land, farmers don't build terraces to prevent erosion.

I agree that it looks like, in making this move, we're only considering one type of soil erosion (by water). So it does seem like the author is failing to consider other reasons farmers might build a terrace to prevent erosion.

However, (A) ends up being not as good an answer as (B) because (B) actually relates to the main conclusion.

The main argument move is the 3rd to 4th sentence.

IF land is flat, THEN farmers don't build T's for erosion.

Contrapositive:
IF farmers DO build T's for erosion, THEN land is not flat.

The author's conclusion is "land is not flat".

So the author's most crucial concern is whether or not he established that "farmers build terraces for erosion".

All he told us is that there ARE terraces.

The crucial missing detail is whether those terraces were built "for erosion".

If we negate (B), we get "NO terraces on farmland in Dooney were built to prevent erosion".

That crushes the move the author was trying to make to reach his final conclusion.

If we negate (A), we get "there are other causes of soil erosion besides water".

One might think this weakens the argument by bringing up OTHER possible causes of erosion, thus OTHER possible reasons for why the farmers built their terraces.

But, crucially, those other possible reasons would STILL BE "building a terrace to prevent erosion".

According to that 3rd sentence, if farmers are building a terrace to prevent erosion (it doesn't specify any TYPE of erosion), then those farmers do NOT have flat land.

So negating (A) and coming up with other types of erosion for which a farmer might build a terrace doesn't hurt the move from 3rd to 4th sentence at all.

Hope this helps.

[drothhello]

Yes friends! The sentence about the water is a red herring!

I was tricked by it like a thief in the night, but now I see the light!

The main point is this: If flat, then farmers don't build terraces to prevent erosion.

The water is irrelevant.

B is the contraposithing.

[CindyL522]

I initially chose C. After reviewing some questions on the form, I came up with a very quick way of solving this problem. I would like to share my thoughts below:

1 All of the A, D , E are too strong. They have the words " only" and " no".

2 Then only B and C left. B says "terraces on farmland in Dooney County were built to prevent soil erosion", which infers that they did it on purpose to prevent erosion. Thus they knew that the farmland in Dooney County is not flat, because flat land does not build terraces to prevent erosion. C kind of means that the terraces were built not on the purpose of preventing the erosion, but just coincidentally prevented the erosion.

[Laura Damone]

I totally agree with you about A, D, E and B.

I would advise eliminating C because we don't actually need terraces to be effective at preventing erosion, we just need them to be built in order to prevent it.