Hi @jorge10rod44, thanks for your post. This question/drill is designed to help you learn formal logic and how to construct an argument from a given premise.
The given premise here is that all Zs are not Cs (Z ==> not C). The contrapositive of this premise is that all Cs are not Zs (C ==> not Z)
The conclusion is "some things that are not Zs are As" (not Z-some-A). "Some" statements are not reversible, but can be flipped. So if not Z-some-A, then you can also say A-some-not Z.
We need to plug in the missing premise.
Answer choice (B) does this. If you add the premise: A-some-C, then you can say: A-some-C==>not Z, which reduces to A-some-not Z, which can be flipped as not Z-some-A.
Hope this helps!
LamontDecember 23, 2021
Aloha, Mehran. My question does this rule apply to all quantifier-type premises? From what I'm understanding from the previous discussion, it seems like all qauntifier premises may be flipped but not negated. Unless the original premise stated that way (A-some-not Z should be flipped to not-Z some A) right?The answer I originally selected I realized should have been flipped not reverse and negated.
jakennedyJanuary 19, 2022
Hi @Lamont,
This applies to all “some” statements, but you cannot reverse a most statement. However, you can turn a "most" statement into a “some” statement and reverse that.
