Q16 - Historian: We can learn about

[deborahc]

In this question, we're looking for a necessary assumption that the argument depends on. I saw the argument core as: if researchers find mercury in his hair, we can conclude the hypothesis is correct (that venereal disease indeed caused his deafness). I narrowed it down to A and B, but chose A. Why is B the better answer?

[ManhattanPrepLSAT1]

Classic Necessary Assumption incorrect answer!

Answer choice (A) is a little too strong. It's not necessary that "none of the mercury can be eliminated," but rather that not all of the mercury can be eliminated.

Using the strategy of negating answer choices to find what is necessary to the argument.

Statements negated:
(A) some of the mercury can be eliminated
(B) All people in Beethoven's time ingested mercury.

If the negation of answer choice (A) were true the conclusion of the argument could still be true - that we could use the presence of mercury to learn about Beethoven's medical history. Remember, when negating answer choices - if the conclusion could still stand, then the assumption wasn't needed.

If the negation of answer choice (B) were true, the conclusion of the argument could not be true. If mercury was ingested by everyone, then the presence of mercury would tell us nothing of the medical history of Beethoven.

I hope this helps! Let me know if it doesn't...

[nanagyanewa]

Thanks for the explanation but could you please explain why D is wrong? Thanks

[andyevans000]

Answer choice D confuses the causation. Mercury isn't the cause of deafness, it's the evidence of VD, which is speculated to cause deafness. As such the argument VD causes deafness, does not rely on D as an assumption.

Try negating the answer. Doesn't so should throw the conclusion into question.

"Mercury poisoning CANNOT cause deafness in people with venereal disease."

The conclusion of the argument is unaffected. Even if mercury poisoning does not cause deafness (for people with VD), venereal disease by itself still could--which is the claim the argument makes.

[sr]

Even if mercury was ingested by everyone that doesn't make the conclusion false. The conclusion depends on the fact that mercury was used to treat veneral disease. It could be the case that EVERYONE had veneral disease at that time and thus everyone took mercury as treatment. If that were true, the conclusion could still be true.

[shaynfernandez]

I must be missing something or... everything.
Answer choice A and B seem absolutely irrelevant to me. I picked D.

How is see the argument is this.
First couple sentences are pointless.

Some hypothesize that venereal disease causes deafness

Some VD --> Deafness

Since mercury was common to ingest to treat venereal disease, we can conclude... VD caused deafness if there is mercury in his hair.

Conclusion: M--> VD
since VD causes deafness we have: VD--> Deafness

so we have a chain if we use answer choice D.

Mercury can cause deafness with VD

M-->VD--> Deafness.

From as a far as i can tell that is about as sound as it gets.

[shaynfernandez]

Also if you negate B. wouldn't some become none because it is the logical opposite.

[timmydoeslsat]

The logical negation of some is none, however, in this context it can be useful to reword the statement.

Negated (B): No people in Beethoven's time did not ingest mercury.

In other words, everyone in Beethoven's time ingested mercury.

This argument reasons in the following manner:

- Some people believe VD caused his deafness.
- Mercury was commonly ingested for to treat VD.
___________________________________________
If we find a trace of mercury, we can conclude that Beethoven's deafness was caused by VD.

This might qualify as one of the worst arguments I have ever seen.

First, we do not know that it is not the case that everyone has mercury in their system. We know that mercury was commonly ingested to treat VD, what else was mercury used for back then? What if everybody had mercury within them?

We would not be able to conclude that finding mercury would prove it.

Second, even if you did know that the guy had VD, you still have not proven that VD caused the deafness in his case. Could he not have been deaf prior to the VD? Could he not have become deaf after having this VD for unrelated reasons? The answer to these questions is yes, he could.

[ManhattanPrepLSAT1]

How is see the argument is this.
First couple sentences are pointless.

Some hypothesize that venereal disease causes deafness

Some VD --> Deafness

Since mercury was common to ingest to treat venereal disease, we can conclude... VD caused deafness if there is mercury in his hair.

Conclusion: M--> VD
since VD causes deafness we have: VD--> Deafness

so we have a chain if we use answer choice D.

Mercury can cause deafness with VD

M-->VD--> Deafness.

From as a far as i can tell that is about as sound as it gets.

Remember that there is a big difference between correlation and causation. This argument is not one where notation will be effective.

The argument's hypothesis is that venereal disease caused Beethoven's deafness. Why? Because if we find mercury in his body, then we would know that Beethoven had a venereal disease. This is, as Timmy pointed out, a terrible argument! First, even if we could prove that Beethoven had a venereal disease, that would not prove that the venereal disease caused his deafness. Second, why would it be true that finding mercury in Beethoven's hair would establish that he had venereal disease?

If the negation of answer choice (B) were true and all people in Beethoven's time did consume mercury, then it could not be established that anyone with mercury also had a venereal disease. It is simply not reasonable to assume that all people in Beethoven's time had a venereal disease, since not everyone in that period was deaf. Since the negation of answer choice (B) attacks the reasoning underlying the historian's argument, it is the correct answer.

Incorrect Answers

(A) need not be assumed. It would be helpful to make sure that we could find the mercury, but the argument doesn't need to find any mercury. The argument only needs the presence of mercury to an indication of the presence of venereal disease.
(C) is too strong. We do not need mercury to be an effective treatment of venereal disease, but simply a prescribed treatment during the time of Beethoven.
(D) undermines the argument by offering an alternative cause for Beethoven's deafness than that hypothesized by the historian (venereal disease).
(E) is irrelevant. The psychological problems of Newton are not related to the argument about Beethoven.

[xmomo]

Just curious: Would D be a valid answer if the question is asking for a sufficient assumption?

Thanks!

[zainrizvi]

I initially focused on negating what I thought was the quantifier (some). In this case, it didn't lead to the correct answer. Should the quantfier have been "some not"?1

[ManhattanPrepLSAT1]

Just curious: Would D be a valid answer if the question is asking for a sufficient assumption?

Answer choice (D) would actually undermine the argument. Remember we don't want mercury to cause Beethoven's deafness but the venereal disease to have caused his deafness. Answer choice (D) provides an alternative cause!

I initially focused on negating what I thought was the quantifier (some). In this case, it didn't lead to the correct answer. Should the quantfier have been "some not"?1

The negation of "some did not" is that "all of them did." If everyone in Beethoven's time ingested mercury, then finding mercury in his system wouldn't prove much of anything!

[WaltGrace1983]

But why would (D) be a good weakener if we had never shown that Beethoven did, in fact, have a venereal disease? The conclusion is a hypothesis stating that "venereal disease caused his deafness." To me, this isn't a simple correlation/causation as we often see because we don't actually KNOW if Beethoven even had venereal disease. Do you see what I mean? There seems to actually be two huge gaps!

This is because, obviously, in order to establish that VD caused deafness in Beethoven, we must actually first establish that Beethoven even had VD (something that he doesn't have obviously couldn't have caused his deafness). After we assume that he had VD, we must assume that VD caused the deafness. So it seems the argument is actually looking more like this:

Mercury was commonly ingested to treat VD
→
If we find mercury, Beethoven had VD
→
VD caused his deafness

So back to (D), I don't think it could weaken because we don't actually know if Beethoven had VD. We assume so, sure but I don't think we can use one assumption (that finding mercury means having VD) to weaken another assumption (that because Beethoven had VD, that caused his deafness). A weakener, as I understand it, must be rooted in a premise or something that is actually true. I think we see these kinds of trap answers all the time on weakeners. I could be wrong though so PLEASE correct me if I am wrong. Whoa I am thinking deeply now!!!

So I understand why (B) is right but I also think it is a super weird answer. I think the LSAT could have taken this a bunch of different ways. How do these necessary assumptions that I made up look?

(A) Finding mercury in one's hair is a reliable indicator that one had VD
(B) VD has the ability to cause deafness (if it doesn't, then who's to say anything about how finding VD would be an indicator of deafness)
(C) There are no other reasons to ingest mercury than to treat a disease (this wouldn't make the conclusion false, but it seems to make the conclusion not follow from the premises, which is the whole point anyway).

What do you guys/girls think?

[uhdang]

Just had a curious negating incident, so wanted to bring it up.

For B), Negation of 'Some did not' would be 'All did.' I get that. But when negating sentences for other questions, I used to just drop "not" and applied negation technique. But in this case, If I just drop "not", it becomes, "Some people in Beethoven's time did ingest mercury." (and this is different from "all people ingest mercury") And when I tried applying this to the argument, it didn't do much to the argument.

Am I missing any rules of thumb like, "you ALWAYS have to apply negation to the modifier (like 'some') and never just drop "not"?

[maryadkins]

When you have a modifier in a sentence, to negate it you want to target the modifier, yes. Also remember that after applying ANY rule, you want to weigh in with your common sense. "Some did" as a negation of "some did not" does not make sense because both of those things can be true at the same time.