December 2013 LSAT Section 2 Question 12

Which one of the following could be the plan for the course, showing the order, from first to last, in which the book...

BibianaM on September 11, 2023

The and/or rule

One of the rules in this one is the and/or rule. In general lets say that the rule is "if NOT A then R and T are chosen" the opposite of this would be "If NOT R OR T then A is chosen" so does that mean that if R is NOT chosen, but T is that A can still be chosen or do both R and T need to not be chosen in order for A to be chosen. This rule just confuses me a little on what happens when only one variable is chosen. Thank you!

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Emil-Kunkin on September 13, 2023

I think your understanding is correct. The only thing that the rule bans is a scenario where N and R/T are all out. The rule tells us nothing about a scenario where n is in. If n is in, it's possible that one of or both of r and t are also in.

BibianaM on September 13, 2023

By N do you mean A?

So for example
Not A ->R + T
Not R or Not T -> A

Does it mean that both R and T DO NOT have to be included in order for A to then be included?
What if I had a scenerio where only one was included:
R was included by T was NOT..could A still be included? I think the word OR is confusing.

Emil-Kunkin on September 15, 2023

In that scenario it totally could. Remember that we only know what would happen if the sufficient condition is true. So, we know that if A is out then both r and t are in, and we know that if either r or t are out, then a is in. This tells us nothing about a scenario where r and a are in. In fact, all three could be in based on that rule.