Supply the missing premise that makes the conclusion follow logically:P: X → not AP: not X → DP: ?C: A → C

pamela24 June 8, 2023

I know it's the same question but...

If A -> C and A -> D then how do we know that C -> D is wrong and D -> C is right aren't they both A?

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Emil-Kunkin June 9, 2023

They are not both A. We are trying to use the premise that If a then d to prove the conclusion that if A then C.

If we know that all As are D, and all Ds are C, that proves that all As are C. We would link it as A then D then C.

We are unable to do this with if C then D. If we know that all As are D, and that all Cs are d, we can't link a and C together, other than by knowing that if something is not D then it is neither a nor c.