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#24 - Must Be True, Author's Perspective

PB410
LSAT Leader
 
Posts: 35
Joined: Sat Apr 01, 2017 4:35 pm
Points: 35

Hi,

I'm not entirely sure why answer choice A is wrong.
I setup the stimulus to be
FPW-----> H and LC
and
(no)H or (no)LC----->FP(is not)W

is A wrong because it is dealing with a different sufficient condition than the one in the stimulus, because Ann kept her promise? I'm kind of struggling to understand the shift from Failure to keep a promise as a condition to someone who kept a promise as a condition.

D is set up as (no)H and (no)LC----->FP(no)W, which is an accurate contrapositive.
Eric Ockert
PowerScore Staff
PowerScore Staff
 
Posts: 164
Joined: Wed Sep 28, 2011 5:46 pm
Points: 148

I think you hit the nail right on the head with the problem on answer (A). It's about keeping a promise rather than failing to keep a promise. Rethink this rule in the stimulus as just a rule ABOUT failed promises. Try this diagram:

Wrong :arrow: Hurt + Lose Confidence

And the contrapositive:

not Hurt OR not Lose Confidence :arrow: not Wrong

So answer (D) hits BOTH of the sufficient conditions in the contrapositive above (it only needed to hit one OR the other) and thus shows that the failure to keep a promise was not Wrong. Bingo.

Answer (A) falls outside the scope of the rule in the stimulus and so we really have no idea whether Ann's kept promise is wrong or not.

Hope that helps!
Eric Ockert
PowerScore LSAT/GMAT/SAT Instructor