If it is not V, then X only if Y

[shc24]

Would someone mind explaining why this =  X V Or Y

I can't figure it out...ughhh

Would really appreciate it!

[shc24]

I figured it out but I just want to see how other people get to it.

Thanks

[Ashley O]

I've never seen wording like that on any LSAT. Where'd you get that from?

[LSAT Eliminator]

I've never seen wording like that on any LSAT. Where'd you get that from?

+1

This isn't from an LSAT. It's probably from some book.

I'd love to hear the explanation for that diagram, too. I don't really think that's the right diagram.

[shc24]

I just realized that I didn't get it.    It's from a lsat workbook and it def right but I don't know how to diagram it.  Can someone please explain? 

[Ashley O]

Read the prior posts. You should write the book company and ask them to defend their explanation. Unless, are you possibly missing some elements in the diagram or did you copy it wrong?

[Jeffort]

I just realized that I didn't get it.    It's from a lsat workbook and it def right but I don't know how to diagram it.  Can someone please explain?  

Based on the vague information you have provided it is unclear what you are asking somebody to explain.  

The statement/logical relationship in the thread title has not appeared in that text form/wording on a modern LSAT.  Where is this from?  Which LSAT workbook (there are many) is it from, is it a drill in the book or presented as a condition in a logic game, did you paraphrase the statement from how it is printed in the book, etc.?  Please supply more context information including which book you found this in (the name of and publisher of the book would be helpful).    

[shc24]

It's one of the study cards provided by Blueprint and actually they answered it for me on their blog @ http://blueprintprep.com/lsatblog/lsat-preparation/why-the-december-lsat-is-so-sneaky/

if you scroll down you'll see it or I can just paste it

 "If it not v, then x only if y – That’s a awesomely complex rule, which game is that from?
Here’s one way to think of that rule – the sufficient condition of this rule is not V, so if V is in we cannot use this rule. So we’re left with two possibilities: either we have V (in which case we can’t go further), or we don’t have V (in which case X only if Y). So you could understand this rule as: V or (X -> Y). (Either we have V, or X only if Y).
That’s one way to represent it (and probably how I would represent it). We can also simplify it a bit by moving the conditional relationship out of the or. If X, then V or Y. In the first representation, we either need V, or else X could be in only if Y – so if X is in, then Y must be in or V (which would satisfy the other half of the Or).
Very tricky." umm

anybody have a different way of explaining it

[Jeffort]

anybody have a different way of explaining it

Yeah.  If you are going to take the December LSAT, forget about this rule and instead spend the remaining two weeks studying, practicing and reviewing with authentic previously administered LSAT questions.  You will not encounter a rule/condition like this in a logic game on a real LSAT. Your time would be better spent thoroughly reviewing conditional logic and the ways it is regularly tested in logic games and logical reasoning problems on administered tests, working on shoring up your current weaknesses as well as building up stamina for the test-day timed conditions.
  

[LSAT Eliminator]

Well, Jeffort is right about ignoring this rule! You won't see that on the LSAT.

What's more troubling to me is that this isn't nearly close to the best diagram (it seems pretty bad to me), and Blueprint seems to be trying to justify their diagram -- well, the first half of the explanation is spot-on, but the remainder seems like more of an attempt to justify it. That's too bad because I normally think of them as having their act together.


The best point made was about V or not V. Based on that, these are the five outcomes under the rule (assuming no other relationships hold outside the rule, including X Y):

When you don't have V:

1. V, X, Y
(if you don't have V, you have to have the other two via X Y)


When you have V:

2. V, X, Y
(once you have V, anything goes with X and Y, including the three below)

3. V, X, Y

4. V, X, Y

5. V, X, Y


So, is it true that X V Or Y ? Based on the five examples above, it looks valid, but  I assure you this is not how we want to diagram this rule on the test. How do I know that? Take the contrapositive:

Rule: X V Or Y

CP: V and Y X

But if we don’t have V, then X Y, so that sufficient condition in the CP can’t occur because you can’t get not V and not Y at the same time. If the contrapositive doesn't work, you've got problems that no one wants to deal with during the LSAT. Not me at least. So, I wouldn’t use that diagram. It would seem the two best diagrams options are:  

V (X Y)

or

V or (X Y)

Either of those seems better and more attuned to the "not V" sufficient idea idea than the one provided as the supposed answer. But that's just my opinion.
 

[shc24]

Well, Jeffort is right about ignoring this rule! You won't see that on the LSAT.

What's more troubling to me is that this isn't nearly close to the best diagram (it seems pretty bad to me), and Blueprint seems to be trying to justify their diagram -- well, the first half of the explanation is spot-on, but the remainder seems like more of an attempt to justify it. That's too bad because I normally think of them as having their act together.


The best point made was about V or not V. Based on that, these are the five outcomes under the rule (assuming no other relationships hold outside the rule, including X Y):

When you don't have V:

1. V, X, Y
(if you don't have V, you have to have the other two via X Y)


When you have V:

2. V, X, Y
(once you have V, anything goes with X and Y, including the three below)

3. V, X, Y

4. V, X, Y

5. V, X, Y


So, is it true that X V Or Y ? Based on the five examples above, it looks valid, but  I assure you this is not how we want to diagram this rule on the test. How do I know that? Take the contrapositive:

Rule: X V Or Y

CP: V and Y X

But if we don’t have V, then X Y, so that sufficient condition in the CP can’t occur because you can’t get not V and not Y at the same time. If the contrapositive doesn't work, you've got problems that no one wants to deal with during the LSAT. Not me at least. So, I wouldn’t use that diagram. It would seem the two best diagrams options are:  

V (X Y)

or

V or (X Y)

Either of those seems better and more attuned to the "not V" sufficient idea idea than the one provided as the supposed answer. But that's just my opinion.
 

Eliminator, THANKS!  Actually, I agree...I understood how that diagram could be justified but my issue with it was the contrapositive.   If not V and not y then not X, but wait it's supposed to be if not V, X only if Y...so yeah I definitely prefer looking at it as V or (if X then Y).


I know it won't be on the lsat but sometimes seeing a problem like that can make you seriously question your abilities.

Thanks for the reply!!

PS I love blueprint.  I have some kaplan material and all the bibles but bp's material is superior but that's just my opinion.

[LSAT Eliminator]

PS I love blueprint.  I have some kaplan material and all the bibles but bp's material is superior but that's just my opinion.

Yeah, I generally think they are good. Powerscore are clearly the trailblazers to me, but I respect BP. In the end, everyone is different and you have to go with what appeals to you.