Hey y’all!
For necessary assumption questions with answer choices that strengthen, when I apply the negation test, would weaken the argument.
How can I tell the difference between an AC that strengthens vs a necessary AC on a necessary assumption question then if the negation test both yields answer choices that weaken?
As I typed this, I realized the answer to my question, can someone confirm please if I’m thinking about this correctly: would an incorrect AC weaken only slightly vs the correct AC completely wreak the argument?
These questions are coming to my mind as I review PT 145 Sect 4 Q 26.
AC A strengthens the argument
AC E also arguably strengthens the argument
AC A negated would be at least one creature that wrecks havoc will be put in the tank, and from the stim, we know creatures that are in the tanks invariably will be deposited when cargo is unloaded at the coasts. Therefore, some environmental havoc is likely at the coast.
If I personalize the argument though, the author could say, “my solution is still better than the current method because there will still be a reduction in environmental havoc wrecked”
E negated though would mean the proposed solution isn’t even viable at all.
Please someone lmk if this way of thinking is how I eliminate strengtheners on necessary assumption questions.
7 comments
Yes, NA negated ACs will completely wreck the argument! They're essentially the absolute bare minimum assumption that the argument needs. But there's another reason why (A) is not correct.
This question is tricky because it buries the main assumption under all of this conversation about the sea creatures. But the skeleton of the stimulus is just: if we use this method A, then we will accomplish our goal. But method A is causing some side effects. One viable way we can avoid side effects is method B. The assumption is that method B will accomplish our goal at least as well as method A, or else there is no point to using method B (even if it might have the side effects).
This is an analogous situation:
I have a cold. If I use this cough syrup, I will feel better. But cough syrup makes me drowsy. One viable way I can avoid drowsiness is by using this pill instead.
The assumption is that if I use the pill, I will also feel better from the cold.
The issue is not whether or not the pill will not be causing drowsiness. Sure, I might not be sleepy from the pill, but it's ignoring the issue at hand: does the pill even help cold symptoms? Maybe it's just a stomach medicine, or a blood pressure medicine, that will do absolutely nothing to help me feel better from the cold.
That's why (A), which says that at least some of the sea creatures won't be able to disturb ecology, is not necessary. It may strengthen the argument, but it is not the absolute bare minimum assumption that is needed!
@haena Hey, Nice to see you again! :) appreciate your post, very helpful especially the analogous argument 🙌🏼🔥
@lagata Haha yes of course! Your questions help me understand the question better too, so I hope you don't mind 😅
Hi! Regarding your question on how to tell the difference between a strengthener and a NA AC, what I think is that the NA AC, negated, destroys the argument, not just weakens it.
For example, in your question PT145.S4.Q26, A negated would say "emptying and refilling midocean would NOT ensure that no sea creatures are pumped into the tanks." Meaning that, there is a possibility, that there could be sea creatures pumped. But even if we negate AC A we know that it wouldn't be a problem for the argument anyways, since the stimulus states that even if sea creatures are pumped they wouldn't survive.
Whereas in AC E, if negated we get "there are NO [some negated is none] ships whose stability could be maintained by refilling their ballast tanks in midocean." If we negate E, the argument isn't just weakened, it completely gets destroyed. Since the stimulus is saying that we should do the filling and emptying midocean, and then we say "hey no ship can actually do that without sinking," then yeah the argument in the stimulus just gets destroyed. How can the stimulus suggest to swap mid-ocean if every ship would just sink?
Good thinking, that's just my take on the ACs, and my approach on NA questions. Hope that helps.
@MarcusTsang Hey Marcus, hope you’re doing good/nice to see you again! :) ✌🏼 Yes, very helpful your post, esp. since this question has really drilled into my mind that the correct AC on a NA negated isn’t simply weakening the argument, the curriculum wasn’t overstating when they said the correct AC would DESTROY the argument.
On a necessary assumption question, your correct answer, based on the stimulus, Must Be True. Your correct answer choice, if negated, must also destroy the support (your premise to conclusion).
I would refrain from thinking of answer choices like strengtheners because a necessary assumption does not necessarily strengthen an argument. A necessary assumption must be necessary but it could make 0 impact on making the conclusion more likely to be true. It's just that when we negate the necessary assumption, the premises no longer support the conclusion, so the argument falls apart.
I find it much easier to think of necessary assumptions using the Must Be True test. You would approach NA questions like a MBT question and you look for something that is supported by the stimulus. To check you can use the negation test and ensure that the negated AC destroys the support structure in the stimulus.
In response to PT145.S4.Q26, I would evaluate A and E as follows:
A - Emptying and refilling an oceangoing ship's ballast tanks in midocean would ensure at least that no sea creatures capable of disturbing the ecology in a new habitat are pumped into the tanks
Must this be true? No, we don't know if "emptying and refilling the tanks would ensure that at least no sea creatures... are pumped into tanks". We don't know anything about "ensuring" or that the tanks are sufficient for having 0 sea creatures pumped. A is hard to support based on the stimulus.
E - There are at least some oceangoing ships whose stability could be adequately maintained while emptying and refilling their ballast tanks in midocean.
Must this be true? Yes. If the ship is carrying these tanks to improve stability and then the author is recommending we do this process that would empty and refill the tanks mid journey, then it must also be true that there are some ships where this process doesn't go against the tanks' objective of improving stability. This is a must be true inference that we can make from the stimulus. If we negate E to say that "there are NO ships whose stability can be maintained while..." then how could it be that we can still do this process while the ship is at sea? Doesn't that go against the whole point of the tanks, which are for improving stability? So that's how the negated version of E would destroy the conclusion.
Now, notice that I didn't say "strengthen" or look at whether the answer choice makes the conclusion more likely to be true when evaluating the necessary assumption answer choices. That's because a NA does not need to strengthen an argument; it just so happens that when we negate the NA it destroys the conclusion (don't confuse with weaken). A necessary assumption is an unstated premise that the argument requires, where taking it away would make the argument fall apart. So, whether that necessary assumption strengthens, weakens, etc doesn't matter when evaluating to find the necessary assumption. What does matter is seeing whether it's entirely necessary for the argument. Ask yourself in each AC, "if this were not the case, does it destroy the argument (make the argument/support fall apart)?"
Hope this helps! Feel free to message if you have more questions!
@DaisukeKaga thank you for your post! Your post is a great reminder that even though necessary questions are grouped with strengthen+weaken, a necessary assumption covers(not makes conclusion more likely to be true) a logic hole created by an assumption made in the argument.