## Difference between Sufficient Assumptions and Necessary Assumptions

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laker

Posts: 9
Joined: Mon Sep 14, 2015 5:52 am

### Difference between Sufficient Assumptions and Necessary Assumptions

Hey there, could anyone give me an explanation for the difference between sufficient assumptions and necessary assumptions? I seem to be getting these mixed up pretty frequently.

Thanks!

Platopus

Posts: 1482
Joined: Mon Feb 13, 2017 11:20 pm

### Re: Difference between Sufficient Assumptions and Necessary Assumptions

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Last edited by Platopus on Sun Dec 17, 2017 4:40 pm, edited 1 time in total.

laker

Posts: 9
Joined: Mon Sep 14, 2015 5:52 am

### Re: Difference between Sufficient Assumptions and Necessary Assumptions

I'm working through the LSAT Trainer right now and I just got to the chapter on sufficient/necessary assumptions. I definitely understand conditional logic, I'm just a little confused on applying it to the assumptions.

My understanding of it:

A sufficient assumption asks you to find an answer choice that, if assumed, would be sufficient to bring about the conclusion.. so Answer choice (true) -> conclusion (correct).

A necessary assumption asks you to find an answer choice that needs to be assumed in order for the argument to work.. so Argument (valid) -> answer choice (true).

Is my understanding correct? Thanks

mmart207

Posts: 222
Joined: Thu Jun 22, 2017 4:40 pm

### Re: Difference between Sufficient Assumptions and Necessary Assumptions

laker wrote:I'm working through the LSAT Trainer right now and I just got to the chapter on sufficient/necessary assumptions. I definitely understand conditional logic, I'm just a little confused on applying it to the assumptions.

My understanding of it:

A sufficient assumption asks you to find an answer choice that, if assumed, would be sufficient to bring about the conclusion.. so Answer choice (true) -> conclusion (correct).

A necessary assumption asks you to find an answer choice that needs to be assumed in order for the argument to work.. so Argument (valid) -> answer choice (true).

Is my understanding correct? Thanks

Think of it as Necessary assumptions giving you half of the arrow that leads to the conclusion being properly drawn, while sufficient assumptions provide you with the entire arrow.

RSolano

Posts: 150
Joined: Fri Jul 14, 2017 1:06 am

### Re: Difference between Sufficient Assumptions and Necessary Assumptions

Sufficient completely bridges the gap or hole in the argument allowing the conclusion to be fully drawn. Pretty easy to predict or pre phrase

Necessary conditions are just anything that has to be assumed for the argument to be valid. If you negate the correct answer for one of these questions it will destroy the argument completely. They're hard to predict or pre phrase because there are so many possibilities down to really obvious stuff.

mmart207

Posts: 222
Joined: Thu Jun 22, 2017 4:40 pm

### Re: Difference between Sufficient Assumptions and Necessary Assumptions

RSolano wrote:Sufficient completely bridges the gap or hole in the argument allowing the conclusion to be fully drawn. Pretty easy to predict or pre phrase

Necessary conditions are just anything that has to be assumed for the argument to be valid. If you negate the correct answer for one of these questions it will destroy the argument completely. They're hard to predict or pre phrase because there are so many possibilities down to really obvious stuff.

I wouldn't say they're hard to predict at all. I find myself predicting the correct answer before I even look at the choices.

RSolano

Posts: 150
Joined: Fri Jul 14, 2017 1:06 am

### Re: Difference between Sufficient Assumptions and Necessary Assumptions

mmart207 wrote:
RSolano wrote:Sufficient completely bridges the gap or hole in the argument allowing the conclusion to be fully drawn. Pretty easy to predict or pre phrase

Necessary conditions are just anything that has to be assumed for the argument to be valid. If you negate the correct answer for one of these questions it will destroy the argument completely. They're hard to predict or pre phrase because there are so many possibilities down to really obvious stuff.

I wouldn't say they're hard to predict at all. I find myself predicting the correct answer before I even look at the choices.

True I guess I should say don't go in with a rigid fixed expectation because sometimes a much broader unexpected right answer can get accidentally eliminated that way.