## Finding the unstated assumption

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Geetar Man

Posts: 564
Joined: Wed May 26, 2010 4:13 am

### Finding the unstated assumption

Does anyone have any good tips on finding the unstated assumption in an argument?
What I've found is that for many of the correct answers, its mostly just trying to find the assumption that the author makes.

Thanks!

Geetar Man

Posts: 564
Joined: Wed May 26, 2010 4:13 am

### Re: Finding the unstated assumption

Geetar Man wrote:Does anyone have any good tips on finding the unstated assumption in an argument?
What I've found is that for many of the correct answers, its mostly just trying to find the assumption that the author makes.

Thanks!

Im basically looking for some ways that people do it when they answer the questions.
I know that people are going to say diagrams and connect the missing pieces, but what I'm trying to figure out is a good way to practice finding the unstated assumptions without necessarily having to diagram them..

suspicious android

Posts: 919
Joined: Tue Feb 09, 2010 4:54 pm

### Re: Finding the unstated assumption

The missing assumption is the reason the argument is bad. That's why I think the best thing to be able to do for any question type is understand why the argument is valid or invalid (vast majority of LSAT questions with arguments are bad).

So, reading the argument, you see why it's a crappy argument, and you say that's wrong because for example, no one cares about xyz. So the author is assuming XYZ is important. Or you say the argument's bad because its an ad hominem. So the author is assuming that the character of the person is relevant to the truth of his statement. Or you say the argument's bad because it confuses necessary and sufficient conditoins. So the author is assuming that what is sufficient is also necessary, or vice versa.

Really, all strengthen, weaken, assumption and (almost all) argument description questions (about 50% of LR questions, if I recall correctly) come down to being able to spot the weakness of the argument. They just ask you to address that weakness in slightly different ways.

Geetar Man

Posts: 564
Joined: Wed May 26, 2010 4:13 am

### Re: Finding the unstated assumption

suspicious android wrote:The missing assumption is the reason the argument is bad. That's why I think the best thing to be able to do for any question type is understand why the argument is valid or invalid (vast majority of LSAT questions with arguments are bad).

So, reading the argument, you see why it's a crappy argument, and you say that's wrong because for example, no one cares about xyz. So the author is assuming XYZ is important. Or you say the argument's bad because its an ad hominem. So the author is assuming that the character of the person is relevant to the truth of his statement. Or you say the argument's bad because it confuses necessary and sufficient conditoins. So the author is assuming that what is sufficient is also necessary, or vice versa.

Really, all strengthen, weaken, assumption and (almost all) argument description questions (about 50% of LR questions, if I recall correctly) come down to being able to spot the weakness of the argument. They just ask you to address that weakness in slightly different ways.

Okay, so what I take from this is that in finding the unstated assumption, one must determine what is wrong with the argument? What about an argument that is valid, for instance? Finding the weakness wouldnt help you on that question since there wouldnt be one.

suspicious android

Posts: 919
Joined: Tue Feb 09, 2010 4:54 pm

### Re: Finding the unstated assumption

By definition, there are no assumptions in a deductively valid argument. In some arguments that we might call good, there are warranted assumptions that can safely be made. Strictly speaking, however, if there is an assumption that must be made for an argument's conclusion to be proven, then the given premises did not prove the conclusion by themselves, and therefore the argument is invalid.

Most arguments that we call "good" are in fact invalid, strictly speaking. That's why it's hard to spot the weakness in many LSAT arguments.

Oh, and just one other thing. You said "To find the assumption of an argument, you must find the weakness in the argument." My general point is, those two activities are essentially the same. It all comes down to understanding why an argument is valid or invalid. When you can see that, answering the questions becomes much, much easier; strengthen, weaken, assumption, whatever.

Edit: Very occasionally, you might get a necessary assumption question on a perfectly valid argument. This is really rare, but it would be something like picking an assumption that logically must follow from a premise. Example:

P: blah, blah
P: Tim is from San Francisco
C: blah, blah

Necessary assumption: Tim is from California

I'm not really sure they ever do this. In general they are looking to see if you can identify the assumptions that bridge the evidence to the conclusion. The above example just shows you understand the broadness of a certain category.

Further edit: In the above example, I think they would use a question stem like "which of the following is required for the argument to be valid", rather than explicitly asking for an assumption. If they were to ask this kind of question. Which they rarely if ever do. In fact, why don't you just ignore this and the previous edit?

KevinP

Posts: 1322
Joined: Sat Sep 26, 2009 8:56 pm

### Re: Finding the unstated assumption

If you have some time, I would recommend reading this: http://www.lsac.org/lsacresources/Resea ... -97-01.asp

Although there isn't anything groundbreaking in the article, I have found a lot of useful information in there.

Geetar Man

Posts: 564
Joined: Wed May 26, 2010 4:13 am

### Re: Finding the unstated assumption

suspicious android wrote:By definition, there are no assumptions in a deductively valid argument. In some arguments that we might call good, there are warranted assumptions that can safely be made. Strictly speaking, however, if there is an assumption that must be made for an argument's conclusion to be proven, then the given premises did not prove the conclusion by themselves, and therefore the argument is invalid.

Most arguments that we call "good" are in fact invalid, strictly speaking. That's why it's hard to spot the weakness in many LSAT arguments.

Oh, and just one other thing. You said "To find the assumption of an argument, you must find the weakness in the argument." My general point is, those two activities are essentially the same. It all comes down to understanding why an argument is valid or invalid. When you can see that, answering the questions becomes much, much easier; strengthen, weaken, assumption, whatever.

Edit: Very occasionally, you might get a necessary assumption question on a perfectly valid argument. This is really rare, but it would be something like picking an assumption that logically must follow from a premise. Example:

P: blah, blah
P: Tim is from San Francisco
C: blah, blah

Necessary assumption: Tim is from California

I'm not really sure they ever do this. In general they are looking to see if you can identify the assumptions that bridge the evidence to the conclusion. The above example just shows you understand the broadness of a certain category.

Further edit: In the above example, I think they would use a question stem like "which of the following is required for the argument to be valid", rather than explicitly asking for an assumption. If they were to ask this kind of question. Which they rarely if ever do. In fact, why don't you just ignore this and the previous edit?

I see, because if there were an unstated premise, then we could use to to undercut the argument. But if an argument is deductively valid, then we wouldn't have any assumptions to undermine. So in day-to-day arguments, there are valid forms of argumentation that present "warranted assumptions" and therefore these assumptions can't be effectively used to undermine an argument, i.e, in an argument, assuming that oxygen is necessary for human survival does not need to be explicitly stated because we just know that its a straight up fact.

I've been practicing this by reading the arguments and posting post it notes that cover the answer choices and writing on the a) what the author seems to be assuming b) what information (relevant to the stimulus) would be helpful to know in order to prove/disprove the author's conclusion. It seems to be helping me, and I hope that by drilling without looking at the answer choices and trying to bridge the gap myself, I will become better at finding the unstated assumption.

I definitely appreciate the feedback Android. It has helped to put things in a much better perspective for me.

Geetar Man

Posts: 564
Joined: Wed May 26, 2010 4:13 am

### Re: Finding the unstated assumption

KevinP wrote:If you have some time, I would recommend reading this: http://www.lsac.org/lsacresources/Resea ... -97-01.asp

Although there isn't anything groundbreaking in the article, I have found a lot of useful information in there.

Dude, I concur! I've only read the first few pages of the article and find some information very useful.

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