Hi all,
I feel as if I have a decent grasp on the different LR question types -- except for Necessary and Sufficient Assumption. For some reason, these just don't click naturally for me, and I even struggle on the Level 2 and 3 questions. I am leaving points on the table by not fully comprehending this topic.
Is there anyone that could explain this to me? I find that the online and even 7sage explanations don't help much and I might need someone else's interpretation of the subject matter to understand it.
Thank you!
3
2 comments
I still get stuck on tricky NA/SA LR questions too! This is how I approach them:
You MUST identify the conclusion. You'll notice that the question stems will ask something like The argument assumes which one of the following (NA) or The conclusion above is properly drawn if which one of the following is assumed (SA)? Every single assumption question is directly integral to the conclusion. If you cannot identify the conclusion, you will have a very hard time identifying the assumption.
BTW, a lot of wrong ACs will target an assumption that might not be relevant to the conclusion. This is on purpose; the arguments are intentionally bad to distract you from the conclusion. The correct answer MUST relate to the conclusion; the wrong answer is not related to the conclusion.
This is a follow up to #1, but you MUST know how to identify the difference between NA/SA question stems.
For NA, the question stem will say things like the conclusion assumes ____, or the argument depends on _____, or the argument requires ____.
For SA, the question stem will say IF ____ is assumed, or IF _____ assumed.
Necessary Assumption Questions
We can divide NA into two types:
Defender Assumptions
Supporter Assumptions (I think 7Sage calls them Link Assumptions. Sufficient Assumption can also be links.)
You can use the negation test for both. Defender assumptions protect the argument from anything that might not allow the conclusion to follow. Usually will sound very weak, very obvious, and very boring. It is the absolute bare minimum that the argument needs.
The street is wet, so it must have rained.
Defender Assumption: A street cleaning truck did not just drive by.
This NA must be true, because if a street cleaning truck DID just drive by, then it gives us reason to think that the wet street is not from rain, but from the truck.
Link Assumptions for NA:
The new city ordinance will increase tax revenue. Therefore, the ordinance will be good for the city.
Link Assumption: An increase in tax revenue is good for the city.
How can we conclude that the ordinance will be good for the city? How do we know what is good for the city in general? The NA must be true because if the increase in tax revenue is bad for the city, then the ordinance will not be good for the city. Our argument is destroyed.
Sufficient Assumption/Pseudo-Sufficient Assumption Questions
SA/PSA will always guarantee/justify the conclusion. It is often strongly worded, powerful, and not boring (can include new information). SA/PSA supplies the trigger that allows the conclusion to follow.
If you eat pizza, you will feel happy. Therefore, John will feel happy today.
Sufficient Assumption: John will eat pizza today.
If John doesn't eat pizza, he might still be happy. But we want something that will guarantee that John will feel happy. Maybe giving him a brownie will make him happy. Maybe giving him a million dollars will make him happy. But the only thing we know for sure is that John eating a pizza will make him happy. So John's gotta eat some pizza!
Note that if you try to negate this, John will NOT eat pizza today, it doesn't mean that he CANNOT be happy today. If he's given that million dollars, there's a good chance that he will be pretty happy! All the SA tells us, is that every time he eats pizza, he will be happy. But it's not necessary for his happiness.
Link Assumptions for SA:
Drinking milk daily is a good source of calcium. Therefore, drinking milk daily can prevent brittle bones.
Link Assumption: Brittle bones is caused by calcium deficiency.
We don't know that there is any relationship between calcium and brittle bones. That's why we need the link assumption, which allows us to conclude that drinking milk -- a good source of calcium -- can prevent brittle bones.
Note that if you try to negate this, brittle bones is NOT caused by calcium deficiency, it doesn't quite destroy our argument. Because maybe drinking milk daily has benefits OTHER than being a good source of calcium that can still prevent brittle bones. Maybe milk contains Chemical X that is not related to calcium but can fortify bones! This is why negation test for SA will not always work.
Hopefully I didn't make any mistakes, but this is how I'd explain SA/NA!
My baseline is 135, aiming for a 155. I study 6 days per week and am off on Sundays. Would you like to work together to learn the concepts?