# Proof by contraposition

From Conservapedia

**Proof by Contraposition** is an indirect mathematical proof for a conditional sentence P=>Q that relies upon the tautology (P=>Q)<=>(~Q=>~P).

## Proof by Contraposition of a Conditional Sentence P=>Q

- Assume ~Q.
- ...
- Therefore, ~P.
- Thus, ~Q=>~P
- Therefore, P=>Q