Necessary Assumptions

iustitia

Someone please help, I still do not know how to do these question types. I have reviewed the curriculum many times, but it is still not sticking.
Any suggestions?

nicole.hopkins

What phase are you at in your prep?

gs556

Necessary assumptions are subtle but crucial.

The number one way LSAT writers will try to trick you on these questions is by fooling you into picking a sufficient assumption.

The best strategy is to negate the answer choices and see what happens to the argument. If the argument can survive, eliminate the answer choice, no matter how tempting it seems. The right answer choice will destroy the argument when negated.

example:

Donald Trump is very popular in red states. Therefore, he will be the republican presidential candidate for 2016.

*NA question stem*

A) Trump is in the lead in the polls
Trump can capture a majority in a national election
C) Trump is extremely popular with the base of republican voters
D) Trump is a citizen of the United States

A, B, and C are all great reasons why the argument might be sound, but D is the only necessary one. If Trump is not a U.S. Citizen, he is not eligible to be elected president and will not be nominated. The argument could still feasibly survive even if A, B or C were NOT true.

nye8870

E) This is gonna be HUGE !!

c.janson35

Yup, definitely use the negation method. It really helps you to see why something is "necessary."

Also something to note: a necessary assumption doesn't have to strengthen an argument, so you may be having a tough time with these questions because you have the wrong mindset. In fact, there can be (and most often are) a bunch of necessary assumptions that must be true for an argument to have any chance at being valid.

For example, in the question above it is absolutely necessary that D be true for the argument to hold; without it, there's no chance that Trump could be the candidate. But there are also a bunch more necessary assumptions that must be true for this argument! For example, before the nominee is selected, it must be true that Trump doesn't withdraw his candidacy, it must be true that Trump doesn't die in a freak toupee accident, and it must also be true that Trump is not abducted by aliens and deposited on another planet without any chance of returning. None of these would strengthen the support-conclusion relationship, but they are all necessary if the conclusion has any chance to be true. (And to prove it, try negating them to see!)

Hope this helps!

iustitia

Thanks guys!!!

I am in the PTing stage!
7Sage community, rocks!

Pacifico

I think JY really does a great job with his bridging/blocking analysis and the more I keep those in mind and pair it with the negation test, the more successful I am during PTs. When I get away from those ideas I tend to wing it in an overconfident manner and pay dearly for it. Sure it's ultimately a crutch but chances are you'll likely need one or two and for my money this is a better one to have.

DumbHollywoodActor

How’s your negating ability? That has to be top notch. If not, I’d review that in the logic section. And I agree with @Pacifico. Keeping “blocking” and “bridging” in the back of my mind for NA really stops me from making a dumb mistake.

ENTJ

@gs556 That's a great example. I especially like your sucker choice in there. People would negate (B) and think...well you have to win the majority of votes in a national election. But not so! The stim talks about the republican primary and not the national election. And even in a national election, you can lose the popular vote and still win through the electoral college.