I'm trying to understand why the following is not a sound inference rule:
Given that NOT P IMPLIES NOT Q, P implies Q.
However, this is a sound rule:
Given NOT P IMPLIES NOT Q, Q implies P.
What did you see when you did truth tables for each of "~P => ~Q" and "P => Q"? Did they have the same truth values, given the same inputs?Given that NOT P IMPLIES NOT Q, P implies Q.