Necessary Assumption Help

Prepare for the LSAT or discuss it with others in this forum.

Posts: 29
Joined: Fri Dec 14, 2012 8:38 pm

Necessary Assumption Help

Postby cause8191 » Wed Jan 02, 2013 6:29 pm

I have had great trouble with determining necessary assumptions. But I think I discovered a few things from drilling them, and I was wondering if I am correct to think this way.

I think that a necessary assumption can be further categorized into subcategories:

1. Assumes causality: Since Ray Lewis is retiring, the Baltimore Ravens won't be any good next year. (The argument assumes that Ray Lewis's retirement will cause the Ravens to be no good next year.)

2. Reaches broad, categorical conclusions without the consideration of other factors: Ray Lewis plays for the Baltimore Ravens. Someone on the Ravens is retiring next year. Therefore, Ray Lewis is the player on the Baltimore Ravens that is retiring next year. (The argument assumes that Ray Lewis must be that player retiring.)

3. States a condition sufficient to reach a conclusion and the conclusion is reached without mentioning the sufficient condition directly: Whenever a great football player retires, his team cannot be a great team anymore. All great football players eventually retire. The Baltimore Ravens are a really great team right now. Ray Lewis plays for the Ravens right now. The Baltimore Ravens will therefore not be a great team anymore. (The argument assumes Ray Lewis is retiring (and/or is a great football player?), which will inhibit the Ravens from being a great team after he retires.)

4. Conclusion is reached based on principle: A great football player is retiring. His former football team therefore can never be successful anymore. (The argument assumes that when a great football player retires, his team will inevitably fail forever afterwards.)

Some arguments can include more than one of these assumptions. #1 and #2 are similar in that they both fail to consider anything else, but differ in that #1 assumes no other reasons exist and #2 assumes that no explanations or factors exist.

This is a little convoluted, but I just need something to look for when I am reading the passages and trying to find the gaps. Do I make any sense?

User avatar

Posts: 190
Joined: Wed Oct 21, 2009 1:07 am

Re: Necessary Assumption Help

Postby joshhoward » Thu Jan 03, 2013 3:09 pm

Your stated assumptions in #1 & #2 are actually conclusions.

#1 assumes that the reason the ravens are good now is because they have ray lewis what you call the assumtion is actually the conclusion.

#2 assumes that ray lewis is the only player on the ravens, or the only player who is able to retire.

#3 you do have correct, except its not and/or. both of the assumptions you identified must be the case.

#4 you have correct.

bp shinners

Posts: 3086
Joined: Wed Mar 16, 2011 7:05 pm

Re: Necessary Assumption Help

Postby bp shinners » Fri Jan 04, 2013 2:50 pm

cause8191 wrote:1. Causal fallacy

2. Exclusivity fallacy

3. Sufficient/Necessary Fallacy

4. Causal fallacy

and my own

5. Equivocation fallacy

What you've listed here are common fallacies committed on LSAT questions. Necessary assumptions very commonly play into the fallacy of the argument. Of those listed, I would say that Exclusivity and Equivocation are the most common on Necessary Assumption questions (and Equivocation fallacies are by a wide margin the mose prevalent in Sufficient Assumption questions), so I would look for those first. The Causal fallacies are usually easy to spot (as there will be a causal conclusion). Sufficient/Necessary fallacies are not too common in Necessary Assumption questions.

Equivocation - look for an answer choice that says there is at least some overlap between the terms being equivocated in the stimulus.
Causal - look for an answer choice that rules out at least one other possible cause
Exclusivity - look for an answer choice that rules out another possibility (strongly related to causal)
Sufficient/Necessary - look for an answer choice that makes it possible to have the sufficient condition (or lack the necessary condition)

Return to “LSAT Prep and Discussion Forum�

Who is online

Users browsing this forum: No registered users and 20 guests