Proof by Contrapositive Is Wrong

1 points by slack3r 11mo ago ↗ HN

Proof by contrapositive is wrong. There is a true, false and undecidable case also.

Let me explain how it works.

p. =>. q. does not necessarily imply not q ==> not p. There are three cases here. If not q is true, then p can also be undecidable.

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apothegm 11mo ago ↗

If p is undecidable in that case, then p ==> q is false. The meaning of the statement p ==> q is that p is never true without q also being true.