Manhattan LSAT logic game question, strategy p. 90

[rob.taboada]

I have a question about one of the conditions of the game found on pg. 90 of the study guide (publishing company published exactly six novels, etc.)-
The first condition states 'exactly one of R's novels was published at some time before either one of Stewarts novels'
To me this reads that the order goes R then both of S then R's second (R-S-S-R). The answer key has R-S then the second R and S are in an unknown order after that (R-S-S-R or R-S-R-S). Can someone explain this to me? The wording seems unclear to me, should I be prepared for similarly worded conditions to have the meaning indicated in the text?
Thanks.

[giladedelman]

Thanks for your question.

Let's work backwards. What does it mean to be "published at some time before either one of Stewart's novels"? Well, as you pointed out, it means that the book in question was published at some time before both of Stewart's novels.

Now, to which book does this constraint apply? It applies to exactly one of Robinson's novels. So, using our translation above, exactly one R comes before both S's.

What does that tell us about the other R? All it tells us is that it doesn't come before both S's, because only one R is allowed to do that. Maybe it comes in between, maybe it comes after both; we don't know. That's why it's either

R-S-S-R or R-S-R-S

Does that answer your question? Let me know if you're still confused.

[rob.taboada]

Thanks for the response. I don't mean to belabor this, but I'd like to get a handle on it. Was this a test question or did this one come from Manhattan?

I guess my hang up is the combination of 'exactly' applying to R and 'either one' applying to S-

That the wording states that exactly (R1) was published before either (S1) or (S2)- that 'exactly' forces R1 and negates R2 before either one of S's novels and the phrase 'either one' applies equally to the individual S1 or S2 and therefore to both S1 and S2 as opposed to both but not necessarily either.

'Exactly one of R's novels (R1, not-R2) was published before either one of S's novels (before either S1 or S2)' = exactly R1 not R2 before S1, exactly R1 not R2 before S2 therefore R1-S1-S2-R2.

I think I understand your explanation, but I read either one to mean 'both' as well as 'each individually'. Does that make sense? Thanks again for walking me through this.

[giladedelman]

No apologies necessary! I can discuss syntax all day.

You are mistaken when you interpret "either" in two ways simultaneously. The constraint, as written, means that R1 comes before S1 AND S2, and that R2 therefore does not come before S1 AND S2.

I understand your thinking: you're thinking, if exactly one comes before either, then the other one doesn't come before either, so it comes after them both. But that's wrong, because the word "either" means something different in those two usages; you need to change the wording in order to properly negate the condition. That is, exactly one R comes before either S; the other R does not come before both S's.

To answer your other question, yes, we wrote this game, but this type of constraint does come up on real logic games, for example this constraint from PT38:

"Frank demonstrates exactly one task before Gladys demonstrates any of the tasks." [In this game each person has two tasks.]

That's almost the exact same thing -- just swap "either" in for "any" -- and I can 100% promise you, from having done (and taught) this game, the constraint is properly interpreted as

F-G-G-F OR F-G-F-G

Does that help?

[rob.taboada]

yes!
many thanks for the explanation- it was like looking at the answer through a fog.