## Setup and Rule Diagrams

jjowens
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The rule that stipulates "Grace helps move the sofa if, but only if, Heather helps move the recliner" (Rule #1) is confusing me.

I'm not sure why this translates into a double-arrow... Why isn't it simply a single directional conditional arrow like the second rule? Also, will all "if, and only if" sentencing structures predicate the double arrow?

Thanks, Joe
Steve Stein
PowerScore Staff

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Hey Joe,

Good question--the phrase "if but only if" is confusing for many students. In fact, I just recently wrote a blog post about this very issue (see http://blog.powerscore.com/lsat/bid/261 ... ut-only-if).

As it turns out, "if but only if" is equivalent to "if and only if."
Consider, for example, the rule "A will go if and only if B goes"
This rule could also be phrased "A will go if but only if B goes"

Regardless which phrasing is chosen, we yield two basic rules:
A will go if B goes; A will go only if B goes.

Including diagrams, it becomes clear that this leads to the double-not arrow:

A will go if B goes (B A)

A will go only if B goes (A B)

Together the two rules yield the double arrow relationship: A B

I hope that's helpful--please let me know whether this clears up this challenging conditional issue--thanks!

~Steve
Steve Stein
PowerScore Test Preparation
jjowens
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That clears it up. Thanks!

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Hi PowerScore,
The explanation for this game makes reference to the Overlap Principle. I am taking the on-line full course and looking for help in locating the discussion of the OP in the lecture materials.

Thanks,
Dave Killoran
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Thanks for the question. It’s in Lesson 4 Homework, on pages 4-28 and 4-29.

Thanks!
Dave Killoran
PowerScore Test Preparation

My LSAT Articles: http://blog.powerscore.com/lsat/author/dave-killoran
PowerScore PodCast: http://www.powerscore.com/lsat/podcast/

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Thank you Dave!
Seriously - you guys and gals rock. Thanks so much for the (always) quick responses!

Dave Killoran
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Dave Killoran
PowerScore Test Preparation

My LSAT Articles: http://blog.powerscore.com/lsat/author/dave-killoran
PowerScore PodCast: http://www.powerscore.com/lsat/podcast/
eveitch
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Any way someone could post a full setup and diagram?
Jonathan Evans
PowerScore Staff

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Hi, Eveitch,

This game is pretty open-ended (i.e. not very deduction heavy), but a baseline setup could look like the following:

I hope this helps!