Isn't X unless Y the same as Y unless X? Forum

[ridiculousness]

Hi Top-Law-Schools forum,

I've searched this on the internet to no avail, but I diagrammed unless statements out and it makes sense VIA DIAGRAM. However, it doesn't make sense intuitively. For example, consider the sentence: If you're in New York, then you're in the US.

To make this an unless statement, we say, You're not in New York unless you're in the US. That makes sense.
However, another unless statement would be, You're in the US unless you're not in New York.

When you diagram out, the second statement is also correct, but how does that make sense? You could be in Los Angeles and still be in the US?

[jerseymike]

Hi Top-Law-Schools forum,

I've searched this on the internet to no avail, but I diagrammed unless statements out and it makes sense VIA DIAGRAM. However, it doesn't make sense intuitively. For example, consider the sentence: If you're in New York, then you're in the US.

To make this an unless statement, we say, You're not in New York unless you're in the US. That makes sense.
However, another unless statement would be, You're in the US unless you're not in New York.

When you diagram out, the second statement is also correct, but how does that make sense? You could be in Los Angeles and still be in the US?

Not the same. Read "unless" as "if not"

Not New York if not US, for example.

[ridiculousness]

Hi Top-Law-Schools forum,

I've searched this on the internet to no avail, but I diagrammed unless statements out and it makes sense VIA DIAGRAM. However, it doesn't make sense intuitively. For example, consider the sentence: If you're in New York, then you're in the US.

To make this an unless statement, we say, You're not in New York unless you're in the US. That makes sense.
However, another unless statement would be, You're in the US unless you're not in New York.

When you diagram out, the second statement is also correct, but how does that make sense? You could be in Los Angeles and still be in the US?

Not the same. Read "unless" as "if not"

Not New York if not US, for example.

Right, so that would make my second statement correct.
You're in the US unless you're NOT in New York.
You're in the US if not NOT in New York.
If New York, then you're in the US.

I just don't see how the first line makes sense, apart from diagramming it.

[LSAT Hacks (Graeme)]

>You're in the US unless you're NOT in New York.

I'm not sure whether this is valid. It's far removed from how any English speaker would ever construct a sentence. LSAT sentences, while complex, match ways that people construct complex sentences in English.

The sentence seems technically true, in that it means "the only times you're not in the US are times you're also not in New York". But it's an odd, odd way to write it, and I don't think it's worth worrying about.

[jerseymike]

Hi Top-Law-Schools forum,

I've searched this on the internet to no avail, but I diagrammed unless statements out and it makes sense VIA DIAGRAM. However, it doesn't make sense intuitively. For example, consider the sentence: If you're in New York, then you're in the US.

To make this an unless statement, we say, You're not in New York unless you're in the US. That makes sense.
However, another unless statement would be, You're in the US unless you're not in New York.

When you diagram out, the second statement is also correct, but how does that make sense? You could be in Los Angeles and still be in the US?

Not the same. Read "unless" as "if not"

Not New York if not US, for example.

Right, so that would make my second statement correct.
You're in the US unless you're NOT in New York.
You're in the US if not NOT in New York.
If New York, then you're in the US.

I just don't see how the first line makes sense, apart from diagramming it.

Sorry, I was confusing myself. In general, X unless Y and Y unless X mean the same thing. Like the poster above said, I think it has to do with language.

[Christine (MLSAT)]

The problem is that you're reading the 'unless' portion as some sort of guarantee, all on its own. We tend to use 'unless' this way in common speech, but it's logically not quite right.

Think of the portion of the sentence *before* the unless as THE PROMISE. The 'unless' portion is the only safe harbor where the promise may not hold (but it might, we just don't know).

So, the statement: "You're not in NY, unless you're in the US" really means that I'm promising that you're NOT in the US. The safe harbor is if you are in the US. If you are in the US, then I don't know whether you are in NY or not, and the promise might not hold. But if we're NOT in the safe harbor (i.e., you're not in the US), then the promise that you're not in NY will hold true. ETA: So, this is essentially saying "you aren't in NY, promise, unless you're in the US (in which case I have no idea if you're in NY or not)".

The same is true for the second statement: "You're in the US, unless you're not in NY". The promise is that you're in the US. The safe harbor is you not being in NY. If we're in the safe harbor (not in NY), then I don't know whether the promise holds - you might or might not be in the US. But if we AREN'T in the safe harbor (you ARE in NY), then the promise must hold. ETA: So, this is essentially saying "you are in the US, promise, unless you're not in NY (in which case I have no idea if you're in the US or not)".

The real upshot here though is that you aren't required on the LSAT to construct unless statements from If/thens, but rather, you'll be taking 'unless' statements and translating them to if/then diagramming. So, you generally don't have to muscle through a weird 'unless' statement that you've constructed that feels wrong. You'll just have to accurately diagram unless statements that they give you.

But yes "X unless Y" is the same as "Y unless X". The first translates to "if not Y, then X", while the second translates to "if not X, then Y", and those are contrapositives of each other - and that means they are logically equivalent.

[schmelling]

.

[simplytea]

I know I'm reviving a basically dead post, but I just wanted to write down my 2 cents before I completely lost it.

What I do when I'm confronted with an "unless" situation, which may be helpful to you or not (hopefully the former), is to negate it. So for instance, the example given is:

You're not in NY unless you're in the US

I just quickly make the positive form of it (easy because I've always been taught that a double negative is a positive) and change it to:

If you're in NY you're in the US

and then contrapositive of that is

If you're not in the US, you're not in NY

To me it's kind of like math--two negatives make a positive. Hope this helps!!

[jaysan150]

I think that's a false reversal . Right ? Like with the first post . Correct me if I am wrong

[KDLMaj]

X unless Y = If ~Y ---> X (contra: ~X --> Y)

Y unless X = If ~X ---> Y (contra ~Y ---> X)

So yes, they're the same thing.

For what it's worth, the LSAT almost never uses "unless" without not/never/etc

So it's virtually always going to be Not X Unless Y (which is just X ---> Y)

(Disclaimer: it's 10am, and I'm super hung over. Take anything I'm saying with a grain of salt)