Setup and Rule Diagrams

[schnappi]

Here is the diagram with all rules and (I think) all deductions. Thanks for help with last two deductions. They truly were a little tricky but beautiful when they came together!

44-3-3.jpg

[nicholaspavic]

Hi shnappi,

Overall, looks pretty good! Thanks for contributing!

[student2020]

Hi PowerScore community!

I just recently purchased the 2020PowerScore Logic Games Bible (and am loving it). But I am doing a games drill and a bit confused.
On page 248, Game#2 - the third rule states: "Exactly one of the sites was discovered by Gallagher, and it dates from the tenth century." In the game answer key that follows (p 251), this rule is interpreted as a conditional: Gonce--> 10. The answer key mentions "there are different ways to represent this rule ..." but just automatically jumps to this. I get that when diagramming it like that it totally helps with the contrapositive inference it provides, but I am just super confused as to how on earth this is to be read as a conditional? Or what were the indicators of this being a conditional statement? How are we to decipher the conditional relationship here in this kind of rule? Are we to always diagram rules that dictate the amount of times a variable is used or where it is assigned as conditional statements? Also, would there be any similar examples of such rules elsewhere/ in other practice tests/a made-up example so I could compare and properly etch it in my memory?

Would really appreciate your guidance!! Thanks in advance,
D.

[Dave Killoran]

Hi PowerScore community!

I just recently purchased the 2020PowerScore Logic Games Bible (and am loving it). But I am doing a games drill and a bit confused.
On page 248, Game#2 - the third rule states: "Exactly one of the sites was discovered by Gallagher, and it dates from the tenth century." In the game answer key that follows (p 251), this rule is interpreted as a conditional: Gonce--> 10. The answer key mentions "there are different ways to represent this rule ..." but just automatically jumps to this. I get that when diagramming it like that it totally helps with the contrapositive inference it provides, but I am just super confused as to how on earth this is to be read as a conditional? Or what were the indicators of this being a conditional statement? How are we to decipher the conditional relationship here in this kind of rule? Are we to always diagram rules that dictate the amount of times a variable is used or where it is assigned as conditional statements? Also, would there be any similar examples of such rules elsewhere/ in other practice tests/a made-up example so I could compare and properly etch it in my memory?

Would really appreciate your guidance!! Thanks in advance,
D.

Hi Student,

Let's parse what this rule is saying, because I suspect that what you threw you off was the fact that this rule doesn't "look" conditional.

Conditionality is typically built around a clearly absolute statement. Is there anything here that is absolute? Yes—"exactly one of the sites" has an absolute characteristic in that it is limited to a single site. So, that's a tipoff here that you might be able to show this as conditional.

Another characteristic of conditionality is that the sufficient condition "tells" or "indicates" that something else has to happen (namely the necessary condition). So, in this game, if I ask you about the site discovered by Gallagher, do you know anything? Yes, definitely, that the site dates from the 10th century. This means that the "Exactly one of the sites was discovered by Gallagher" is a sufficient condition, and the remainder is a necessary condition.

The broader rule to be drawn here is about how absolutes work, and how they can be "hidden" inside a statement that doesn't use the traditional "if," "all, "every, " type of indicators. Because of this, you can't make a conclusion that every rule about dates would be conditional. This is the beauty of the LSAT—you have to learn the underlying logic of statements like this, but when you do it makes you stronger and stronger, and better prepared for the next test you take

Thanks!

[student2020]

Thank-you so much for the prompt reply! So helpful!
Cheers!

[Tajadas]

Hi all,

I really appreciate your explanations of how using "than... either" means that Rule 5 indicates Site 3 dates from a more recent century than both Site 1 and Site 4.

My question is: How would Rule 5 have been phrased if LSAC wanted the rule to indicate Site 3 dates from a more recent century than either Site 1 or Site 4? I can't seem to imagine a way for Rule 5 to indicate this without using "than" and thus falling into the implied "both" mentioned in my first paragraph.

[Jeremy Press]

Hi Tajadas,

That's a great question! While there are often multiple ways to express the same relationship, here's one possible unambiguous way for them to phrase a rule like you're thinking of: "The site visited third dates from a more recent century than does the site visited first or that visited fourth, but not both." Ordinarily when the test writers want us to exclude the possibility (or the certainty) of both, they'll add that "but not both" qualification.

Hope this helps!

Jeremy

[leslie7]

Sufficiency/Necessity Triggers

Hello,

I was just wondering from the "trigger" words how we would know that

"Exactly one of the sites was discovered by Gallagher and it dates from the tenth century" is a conditional?

G1-->10 , /10--->/G1

apart from trigger words e.g. if, only etc? How can we interpret LSAT questions that do not have those key words and know when to draw it as a conditional? TY!

[KelseyWoods]

Hi Leslie!

While the conditional indicator words are helpful, it's most important to think about the overall relationship. A conditional relationship is one in which you have something that is enough or sufficient to indicate that something else must also be true/occur. Or, another way to think about it, a relationship in which one thing is necessary for another. It also might help to just think about it as a relationship in which you could reword it in if/then terms without changing the meaning of the statement.

So this rule states: "Exactly one of the sites was discovered by Gallagher and it dates from the tenth century"

That means that IF a site was discovered by G, THEN it must be from the 10th century. Likewise, IF a site was not discovered in the 10th century, THEN it cannot be discovered by G. Phrasing it as an if/then statement in this way does not change the meaning of the relationship as stated in the original rule.

Ultimately, you don't necessarily have to diagram this as a conditional rule. You could do it as a block rule and you would be able to make the same inferences from it. But the more comfortable you get with conditional reasoning, the easier it will be for you to apply it in situations in which you have to rely more on the precise nature of the relationship rather than the conditional indicator words.

Hope this helps!

Best,
Kelsey

[Stephanie Oswalt]

Hi!

We received the following question from a student. An instructor will respond below.

Hello,
On Advanced Linear Game #2 rule #4 pp.248 (LGB 2022) states that “If a site dates from the eighth century, it was discovered by Oliphant.” What would the contrapositive be?

Would it be that if it was not discovered by Oliphant, then the site does not date from the 8th century?

Thanks!