## "Necessary occurs before" 2017 LGB. pg. 57

Stephanie Turaj
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We recently received the following question from a student. An instructor will respond below. Thanks!

Hi, I have the 2017 LGB. In Pg 57, side note "Necessary occurs before", isn't the example incorrect?...
Dave Killoran
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Hi,

Thanks for the question! The "Necessary occurs before" example there is:

"To reach the top of the building, one must climb."

In this case, you'd be looking at a diagram such as the following:

Top of building Climb Stairs

In that case, you'd be climbing the stairs on the way to the top of the building, and thus chronologically the climbing would occur before satisfying the sufficient condition of reaching the top of the building.

Please let me know if that helps. Thanks!
Dave Killoran
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Tomjwc
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I'm still a bit confused. If the necessary condition occurs before, shouldn't it be

climb--> reached top of the building?
Tomjwc
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I guess my question is, in what sense is the necessary condition occurring before?
Dave Killoran
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Ahh, gotcha. If you look at the way things are being discussed there, we are talking about chronologically. So, what comes first in time (because where the conditions occur in the sentence is irrelevant). In this particular example, to get to the top of the building you would first have to climb the stairs, and thus climbing (the necessary condition) would occur before reaching the top of the building (the sufficient condition). Does that help?

Dave Killoran
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mvarkey
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Could you also please explain the "Necessary Occurs After" example? Isn't the necessary part of the statement, "win the war"? Wouldn't that have to occur before we get world peace?
Dave Killoran
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mvarkey wrote:Could you also please explain the "Necessary Occurs After" example? Isn't the necessary part of the statement, "win the war"? Wouldn't that have to occur before we get world peace?

Sure, happy to explain!

In the example, "we win the war" is preceded by "if," which is a sufficient condition. So, the diagram for that would be:

win the war world peace

Thus, you win the war and after that peace follows. Hence, the occurrence of the necessary condition is chronologically after the occurrence of the sufficient condition.

Please let me know if that helps. Thanks!
Dave Killoran
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My LSAT Articles: http://blog.powerscore.com/lsat/author/dave-killoran
Stephanie Turaj
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An instructor will respond below.

Thanks!

Hi there,

I'm on chapter 3 of the Logic Games Bible and am a bit confused about the side note on page 57, that states that a necessary condition can occur before, at the same time, or after the sufficient condition. Specifically,

"Necessary occurs before: To reach the top of the building, one must climb the stairs"

When I read this sentence, I see the words "must" and "to", which according to the chart on page 60, actually indicate that "climb the stairs" should be the necessary condition and "reach the top of the building" should be the sufficient condition. How is this an example of "necessary occurs before"?

I also tried mapping the above sentence to the human/mammal and the A+/study examples which logically would equate to,

"To be human, one must be a mammal." & "To get and A+, one must study"

Again these are statements where the necessary conditions occur after not before.

Any clarification would be deeply appreciated! I know conditional statements are critical to both logic games and logical reasoning so I want to make sure I understand this concept.

Matt
Jon Denning
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Hi Matt - great questions!

Before I get into a response to them, however, let me pay you two quick compliments:

First, you've got the idea exactly right here, as your rephrased human/mammal and A+/study sentences are spot on! And that ability to recognize consistencies in meaning despite variations in appearance/phrasing is key on this test. So that's extremely encouraging!

Second, this degree of scrutiny and attention to detail—both in terms of linguistic subtleties and nuance (and minutiae), as well as in the book itself as you consider sidebar notes—is the hallmark of both big improvements and high scores. So keep that up and you'll find it really rewards you on test day

Now, to your questions about sufficient and necessary condition ordering. I think some of the confusion arises from unintended ambiguities in the words "before" and "after," as they can mean (at least) two potential things in this context: before/after in terms of sentence placement/construction; before/after in terms of real-life event timing (chronology).

What the book is referring to is the latter usage, where necessary conditions can happen at some point in time before the sufficient, or at some point in time after the sufficient. The "stairs" example illustrates this nicely, as the necessary condition "climb the stairs" must clearly occur prior to reaching the roof, and thus the necessary piece was the first event to actually take place!

Ditto the A+/study example: studying is necessary, but it occurs before someone takes the test (and certainly before they get a grade back).

So in the same way that sufficient and necessary conditions can appear in any order in a given sentence, so too can they occur in any order relative to the real-world passage of time.

The reason we make that explicit is because (1) people often (wrongly) assume that the condition that is given ahead of the arrow in the conditional relationship (the first piece) must have preceded the condition after the arrow, but that assumption is false and when used to construct conditional diagrams will get you into a lot of trouble! (sometimes people go in the opposite direction and mistakenly assign the first-occurring event as the sufficient condition, but it comes to the same thing), and (2) the other major reasoning type on the LSAT, Causality, has conditions that DO occur in a particular temporal sequence, since the cause must always precede the effect in order for the cause to make the effect happen. And since conditional reasoning and causal reasoning are so often confused, we highlight that particular distinction as one more way—and of course one more reason—to keep them separate from one another.

I hope that helps clear things up, but if you have any further questions by all means let me know and I'll do what I can to continue clarifying. Thanks!
Jon Denning
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