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Hey guys,
I'm having trouble understanding question 8 from PT4 section 1. I diagrammed it:
-PWP ---> -GLS and realized that the passage makes an illegal reverse. It should have been GLS ---> PWP (the contrapositive) instead of PWP---> GLS. However, even with that in mind, I wasn't able to find the right answer. Now, I don't understand why D is the right answer. Can someone please help me?
Cheers!
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Thank you so much mates!!!!!
Hi!
You're right that the conclusion is an illegal reversal. By saying PWP --> GLS, the conclusion mistakenly states that PWP is the sufficient condition and that GLS is the necessary condition. (D) reflects this.
The problem with the stimulus is not that it makes a wrongful reversal, but that it makes a wrongful negation. You are kind of right, however, as those two errors tend to go hand-in-hand: both wrongful reversal and wrongful negation assume that A ---> B and B ---> A.
The stimulus says that, since ~PWP ---> ~GLS, PWP ---> GLS. The contrapositive of the stimulus is GLS ---> PWP, however. So the argument assumes its own conclusion without justification. This is what (D) points out: the argument assumes PWP is sufficient for GLS.