June 2010 LSAT Section 5 Question 18

Based on the passage, it can be concluded that the author and Broyles-González hold essentially the same attitude toward

CheVaughn on January 3 at 05:01AM

Argument Completion Drill A—>C Not B-M-not C

I am having some trouble understanding why the answer is not no valid conclusion in the argument completion drill. I kind of understand how the answer is not B-s- not A; however, I thought you could not have an arrow pointing to a quantifier? How do you know when to do a contra positive and when not to?

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Emil-Kunkin on January 3 at 04:11PM

Personally, I really dislike the approach to diagraming most and some statements, although it certainly does work for many people. I'll try to walk through how this makes sense to me, which I suspect may be a more common sense approach.

We know that all As are C. If you are from Anaheim, you are from California. This also means that if you are not from CA, you are not from A.

We also know that most things that are not b also are not c. We know however that saying not from Ca guarantees not being from Anaheim, so we can simply sub in not A for not C.

If you find this confusing you're not alone. I really struggle with such abstracted pure logic, and I generally find it much easier to approach real questions which have related concepts (like ca and Anaheim) than just as bs and cs.