Q23 - Art Historian: This painting, purportedly by Mary Cass

[Emily Madan]

PT68, S3, Q23 (Necessary Assumption)

(B) is correct

As a necessary assumption question, we need to identify something that is vital to the reasoning of the argument core. It may or may not be sufficient to prove the conclusion true, but without it, the logic of the argument falls apart.

In this argument there is a lot of information, but much of it is background. Let’s start by identifying the conclusion and what is relevant to the conclusion. Here, our conclusion is that the painting is not a Cassatt. The only evidence that seems to support this is that the brush style is unique among the Cassatt paintings. Combining those ideas, our argument core of this question is:

The brush style of this painting is not
found in any other of Cassatt’s works.

--->

This painting is definitely not a Cassatt


It seems like there’s a fairly significant assumption here. Shouldn’t it be possible that Cassatt choose to use a unique brush style in this painting? The author has to be assuming that Cassatt couldn’t be unique in this respect or at least on this painting.

(A) This doesn’t talk about the argument core, but about the pieces of evidence that imply it could be a Cassatt. Eliminate it.

(B) This does talk about the brush style, but is filled with negatives, making it hard to understand, so let’s leave it for now.

(C) This answer choice is about the subject matter, which is irrelevant to the argument core. Eliminate it.

(D) This answer choice also talks about her brush style, so let’s leave it.

(E) This answer choice is also about brush style, but it talks about other artists mimicking Cassatt’s style. We need something that says Cassatt wouldn’t have changed her brush style. Eliminate it.

We’re left with (B) and (D). Since this is a necessary assumption question, we can test each with the negation test. We can negate (B) by saying that some of Cassatt’s works are painted using a brush style that is not exhibited in any of her known works. If this is true, then the brush style being different doesn’t say anything about whether Cassatt painted this piece. This seems like a perfect necessary assumption, but let’s negate (D) to be sure.

Negated (D) would say that the most characteristic feature of Cassatt’s work is not her brush style. If this is true, the logic of the argument still holds. The brush stroke may or may not be her most characteristic feature, but that doesn’t affect whether a different brush style means this piece is not her work. (D) is not a necessary assumption, so we can confidently choose (B).

[ECMH05]

I eliminated all of the answer choices down to B and D for this question but ultimately chose D.

I think one of the main concepts of sufficient and necessary assumptions that sometimes trips me up is the notion that it is possible for an answer choice to be too strong for the question. That is, the answer choice would answer choice would be correct for a sufficient assumption question but not a necessary assumption question. I may be mistaken but I gathered this from the study guide. Maybe a re-read of that chapter is overdue.

I knew answer choice B was the strongest answer choice but because I had the above in mind I suppose I illogically choice D.

I know in the LR book it states that sufficient and necessary conditions are not mutually exclusive and that's where my confusion lay. h

Can anyone clear this up for me generally and in regards to this question?

Thanks!

[christine.defenbaugh]

ECMH05, I'm so glad that you're thinking about the complex relationship between necessary and sufficient assumptions! It can be a difficult thing to wrap your head around, and it's a critical concept to be comfortable with.

First, let's break down that relationship. You seem to be categorizing sufficient assumptions as 'stronger' and necessary assumptions as 'weaker'. There's some truth to that idea as a general matter, but it is not a rule, and you cannot use it as an elimination technique.

A sufficient assumption will either build a bridge right from the premises to the conclusion and stop, or it will build a bridge to the conclusion and keep going! Both will successfully get us to the conclusion. A necessary assumption may be the complete bridge, or it may just be one critical stone in the bridge. In either case, taking it away (negating it!) would leave you stranded at the premise, with no way to get over to the conclusion.

So, sufficient assumptions are not always stronger than necessary assumptions. They simply perform a different task. Sufficient assumptions will always get the job done (of getting us to the conclusion). Necessary assumptions are the thing we just can't do without.

The best practical advice that I can give you is to treat necessary and sufficient assumptions as two entirely separate issues. It's critical to realize that not every Necessary Assumption question will have a 'sufficient-but-not-necessary' trap answer! Many of them don't. So if you've got it narrowed down to two answers, it often won't be one necessary and one sufficient assumption! Also, the correct answer may itself be sufficient!

So how can you sort it all out? By staying focused on only the task in front of you! When you are tackling a Necessary Assumption question, don't worry about sufficiency. Eliminate answers you know are out of scope, then apply the negation test and see which negated answer throws the argument off a cliff!

Please let me know if this answers your question completely!

[csunnerberg13]

I took the core to be including both the part about the brush style not found in her other work and the fact that the other materials are consistent with most of her work as the two premises...which makes A seem pretty good. It seems necessary here that no one else could acquire those materials because, if they could, how would we guarantee it's a forgery? So what's the issue with A, unless I was supposed to exclude the premise about consistent materials. In that case, I guess my question is why would I exclude that and how do you know it should be excluded?

[ttunden]

D is really strong. In Necessary Assumption questions you have to be wary of strong answer choices.

Is it absolutely required that the most characteristic feature of Cassatt's work is her brushstyle? does the author ABSOLUTELY have to assume this? no.

B is better because its a bit softer and it really does pass the negation technique. I negated it by replacing none with some. Anyways, even if you did negate D it wouldn't destroy the argument. Okay so it isn't the most characteristic feature, maybe its the 3rd or 4th most important feature. Does that destroy the argument? no. Whereas if you replace none with some for B, it would hurt the argument a lot. It would make the historian not able to derive his conclusion. Would make him second guess.

[AnnaC659]

Hi,

I also had the same question as csunnerberg13 above.

So I was left with (A) and (B) but chose (B) because of the words "readily available" in (A). I thought it could have been difficult for others to find certain canvas and materials that Cassatt was using, hence not "readily available," but that doesn't necessarily mean that they couldn't obtain them at all.

Is this correct?
Thank you

[HughM388]

Hi,

I also had the same question as csunnerberg13 above.

So I was left with (A) and (B) but chose (B) because of the words "readily available" in (A). I thought it could have been difficult for others to find certain canvas and materials that Cassatt was using, hence not "readily available," but that doesn't necessarily mean that they couldn't obtain them at all.

Is this correct?
Thank you

I have the same question. Regardless of the "core," the argument is that the painting is a forgery—that is, it was painted by someone other than Cassatt. For someone other than Cassatt to have painted the painting in question, which admittedly uses the typical Cassatt materials, that someone else would have to have had access to those same materials. But if no one else had access (ready or otherwise) to those materials—if only Cassatt had access to those materials—then no one but Cassatt could have painted the painting; and it is therefore not a forgery. Unless other people had access to the same materials, the argument disintegrates.