Necessary Assumption fuck-ups

maitaisp

So in my mind I attack NA questions pretty methodically: negating each answer choice and determining which one wrecks the argument, while also taking into consideration the bridge and shield types of assumptions that I learned about here (and the powerscore lessons too for that matter). I'm still fucking up. I've corrected my earlier mistake, where I tended to conflate SA and NA questions, but I'm still missing a significant number. Is anyone else having this problem? Any advice?

Nilesh S

gets better with BR and time

polscken

Jonathan explained it like this to me...picture a pothole. You have to fill the pothole with your argument. For NA all you need to fill is a tiny little part of the pothole, but that part is necessary for the rest to be filled in. For SA you have the fill the whole pothole. It doesn't matter if you overfill.

maitaisp

Yeah just have to keep at it, and I'll keep that image in mind polscken. Thanks guys!

mjjohns6

NECESSARY ASSUMPTION QUESTIONS
HOW TO FIND NECESSARY ASSUMPTIONS Lesson 1 of 23
“I play basketball. Therefore, I am one of the best basketball players in the world.”
SA (declare argument valid)
Wow the MVP 10 years in a row
I’m a beast
**Almost perfect argument u could hope for. (You don’t need any of them)


NA (subtle, it gets little done)I know how to dribble
I am alive
*Crappy argument yet they are all necessary. (You need all of the above) u can have 100 NAs and still have a crappy argument. But if u throw one of them away your argument is screwed.


HOW TO FIND NECESSARY ASSUMPTIONS 2 Lesson 2 of 23
P1 + P2 → C (Valid argument)
P1 + P2 - - - > C(not valid)
P1 + P2 + SA → C (valid)
[P1 + P2 + SA → C ] → NA (Valid argument (VA) → NA)
VA→ NA
/NA → /VA

HOW TO FIND NECESSARY ASSUMPTIONS 3 Lesson 3 of 23
VA→ NA
/NA → /VA
_____________________
Two test from these two
1. MBT
2. Negation- try to negate the answer choice, if you negate the right answer choice you will wreck your argument.
NA:
1. Blocking: protect something
2. Bridging: To get you from point A to point B
I know strategy. Therefore, I am one of the best generals I the world.
• Bridging: knowing strategy is somewhat relevant to being the best general in the world. Very subtle statements.
• Blocking: protect argument from wrecking balls coming in from all directions. Trying to knock down your argument.
o “Men that you command don’t respect you. You’re psychotic”
o To block u say you’re not psychotic, men do listen to you, you’re not crazy.

NA- STRENGTHEN-PSA-SA QUESTIONS Lesson 4 of 23
NA________STRENGTHEN_____________________PSA_________SA
NA: prevents you from dying. Harding any support.


HOW TO APPROACH NECESSARY ASSUMPTIONS QUESTIONS Lesson 5 of 23
Necessary assumptions can wreck an argument.
First, let’s understand what a necessary assumption is. It’s an assumption (definition: unstated premise) that is necessary for the argument. “Necessary” here means the same thing it does when we talk about a “necessary condition” (as opposed to a “sufficient condition”). Let’s put the relationship between argument and necessary assumption in Lawgic and then run the contrapositive.

Argument (valid) –> Necessary Assumption (true)
/Necessary Assumption –> /Argument
• In English, this means that when we negate the necessary assumption, the argument falls apart. No necessary assumption, no argument.
• Necessary Assumption questions present you with an argument (premises + conclusion) where in order for the conclusion to be valid, there is a necessary (critical) assumption not stated in the argument. Without this particular assumption, the argument falls apart. Your job is to find this sucker, a necessary assumption, in the answer choice.
There are two types of Necessary Assumptions (NA).
• NA Question Type I: The Shield
Consider a simple argument:
As trees age, they grow rings. Therefore, counting the number of rings a tree has will tell us how old a tree is.
• Before we get into necessary assumptions, let’s establish a point of comparison with sufficient assumptions. What are some sufficient assumptions we can make this argument valid? How about trees grow 1 ring per year? That will make our argument valid. Given this new information, we can say that it must be true that counting the number of rings a tree has will tell us how old a tree is. Because we know that as trees age, they grow 1 ring per year.
• But is this sufficient assumption (that “trees grow 1 ring per year”) a necessary assumption? Well, is it necessary? Let’s negate it to see if it wrecks the argument: It’s not the case that trees grow 1 ring per year. Okay, so does this wreck our argument? Well, no. Because so what if trees don’t grow 1 ring per year. Maybe trees grow 3 rings a year, or .5 rings a year. Or whatever. As long as it’s a function of time, we can determine how old a tree is by counting its rings. So, I hope you see that while “trees grow 1 ring per year” is a sufficient assumption, it’s not a necessary assumption. Given the additional premise of trees grow 1 ring per year, our argument becomes valid. But, we can also say trees grow 4 rings a year, which would also be sufficient. For this argument there are plenty of sufficient, but not necessary assumptions.
• Let’s consider now a necessary assumption. Trees don’t skip its ring growth every once in a while. Is this necessary? Let’s see what happens when we negate it: trees do skip its ring growth every once in a while. Well, there goes our argument. How are we supposed to reach our conclusion from our premise if this negated statement is true? We can’t. Our argument is destroyed. It falls apart. If trees skip its growth rings every once in a while, there’s no way that we’ll be able to tell how old trees are by counting its rings. The assumption that trees don’t skip its ring growth every once in a while is necessary. What else is necessary? That trees don’t grow additional rings during years with lots of rain. Answers to shield type necessary assumption questions protect your argument from being wrecked.

NA Question Type II: The Bridge
• Just as the name suggests, these answer choices point out gaps in the logic of the argument. For example, the major premise of the argument might tell you: you edge out your fiercest competitor in a race. The conclusion then claims that you win the race.
• The argument has jumped from one idea (beating your fiercest competitor) to another (winning the race). Bridge questions trade on your inclination to conflate two different ideas. They’re assuming that your fiercest competitor was the only competitor that had a shot of beating you. What about all the other guys? Maybe the dark horse will be the one to win the race. The necessary assumption here may say something that edging out your fiercest competitor is in some way relevant to your winning the race.
• Think about building a bridge. The premises left you at one side of the river and the conclusion is way over on the other side. It’s your job to find this bridge in the answer choice that takes you from the premise to the conclusion.