"Logic? who needs that froo-froo, stuff anyway? It all just comes down to semantics." I have heard such sentiments from a variety of people. But the fact is that we all need logic and use it every day.
De Morgan's rules go as follows:
- not (P and Q) = (not P) or (not Q)
- not (P or Q) = (not P) and (not Q)
More broadly, why do we need logic? We need it in order to sort out complex problems and, hopefully, formulate solutions.