## Could someone explain the concept of Unless/Except?

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ioannisk

Posts: 83
Joined: Wed Jul 31, 2013 11:38 am

### Could someone explain the concept of Unless/Except?

I can figure out unless/except mechanically. I know to mentally change "unless" to "if not"
BUT
I do not understand unless/except conceptually/abstractly. For example, I can understand why a statement like "all dogs smell bad" cna lead to sufficient: Dogs necessary: smell bad because the statement is telling you if it is a dog, it must smell bad.

But I don't understand, conceptually/abstractly, how "i am tired unless i slept" would lead to NOT slept --> I am tired. In my mind, it actually makes more sense to have the opposite I slept ----> not tired, because, to me, the statement sounds like you can assume the person is tired unless he slept, so if he slept you can assume he isn't tired. I know that is wrong inference but conceptually/abstractly, that makes sense to me.

Could someone help me out?

Thanks.

KingofSplitters55

Posts: 139
Joined: Sun May 13, 2012 7:40 pm

### Re: Could someone explain the concept of Unless/Except?

"Unless X, then -Y"

X is a necessary condition for Y. If Y exists, then X has to have happened. However just because X exists doesn't necessarily mean that Y happens.

For example:

"I can't be in Berlin unless I'm in Germany"

Being in Germany is a necessary condition for being in Berlin. If you are in Berlin, you know you'll also be in Germany. However being in Germany does not signify you are automatically in Berlin.

Diagrammed, it would be:

(Berlin) -> (Germany)
(Suff) -> (Necc)

In the case of your example, sleeping is a necessary condition for not being tired.

Indeed it takes some 'translating' it and sometimes the specific syntax can really throw you for a doozy. Once you have gotten down the few different ways unless/perhaps/except can be expressed, then you'll be able to recall and translate it much easier when you encounter such statements.
Last edited by KingofSplitters55 on Sat Sep 14, 2013 2:24 pm, edited 1 time in total.

neprep

Posts: 1066
Joined: Fri Jul 26, 2013 11:16 pm

### Re: Could someone explain the concept of Unless/Except?

ioannisk wrote:I can figure out unless/except mechanically. I know to mentally change "unless" to "if not"
BUT
I do not understand unless/except conceptually/abstractly. For example, I can understand why a statement like "all dogs smell bad" cna lead to sufficient: Dogs necessary: smell bad because the statement is telling you if it is a dog, it must smell bad.

But I don't understand, conceptually/abstractly, how "i am tired unless i slept" would lead to NOT slept --> I am tired. In my mind, it actually makes more sense to have the opposite I slept ----> not tired, because, to me, the statement sounds like you can assume the person is tired unless he slept, so if he slept you can assume he isn't tired. I know that is wrong inference but conceptually/abstractly, that makes sense to me.

Could someone help me out?

Thanks.

Technically: sleeping is a necessary condition for not being tired in your argument, not a sufficient one. But I know this isn't what you're looking for.

Abstractly:
This statement is actually true for me, in that, I can say that I am tired unless I sleep for at least 8 hours every night. But other things can also make me tired: For example, last night I slept 8 hours, but then I took an LSAT PrepTest and graded 40 problem sets for my TA job, after running 10 miles. Now, even though I slept, you cannot assume that I am not tired, because all this other stuff happened and I am, indeed, very tired. Even though I slept the requisite amount.

meegee

Posts: 144
Joined: Mon Apr 01, 2013 9:00 pm

### Re: Could someone explain the concept of Unless/Except?

I had some trouble with except and unless. For some reason, the books didn't really do it for me.

And then I read about "except" and "unless" in the LSAT Blog by Steve.

Read it, it simplifies it and makes it so easy.

To very quickly summarize, unless is a necessary indicator. So whatever comes after unless, will be on the right side of the arrow diagram. The other part will be the sufficient, and will be on the left side of the diagram. But we're not done! Because of "unless" we also have to negate the sufficient. Then our diagram is complete.

I am not a banana unless I'm a lamp.
Step 1) "Unless" is a necessary indicator. So far we have this: ______ --> lamp
Step 2) The other part is the sufficient. So we have this: not banana --> lamp
Step 3) We have to negate the sufficient. So we get this: banana --> lamp.
If I am a banana, I'm a lamp.

The table flies unless the door is crying.
Repeat above steps.
Step 1) _____ --> door crying
Step 2) table flies --> door crying
Step 3) table NOT flies --> door crying
If the table is not flying, the door is crying.

I'm still pretty shitty with my LR, so if I'm wrong, someone please point it out and correct me.