LG Bible pg 149 question 23 Forum

[petrovovitch@]

I solved this question by elimination, which is the method suggested by the bible, but I eliminated D and E for different reasons than they suggest. In fact reasons plural is wrong, I eliminated both D and E for 1 reason.

I'd like to expound a little on this reason.

I eliminated both D and E because they are "isomorphic" (bear with me - I'm a math major). What this means is that they are the same answer and hence since 1 of them being the correct answer would imply that the other is as well they both are false.

Why are they both the same answer? Because in the given rules no single variable is singled out (this is a pattern game after all) and hence S,U, and R were chosen to be the variables discussed, in these 2 answers, arbitrarily. The 4 variables discussed (S,U,U,R) could have been any four (R,S,Q,T) or any 3 (T,Q,Q,R) and these answers would still have the same implications.

Incidentally A and B can be eliminated by the similar reasoning.

Hence C is the answer without constructing any hypotheticals.

Moral: When the global rules don't single out any variables and an answer to a global "must be true" question with no conditional does, it's probably(hedging my bets) wrong.

If this isn't clear I'll be back later to explain further.