FOC I - 4.6 Indirect Argument: Contradiction and Contraposition

Method of Proof by Contradiciton

also known as reductio, impossibile or reductio ad absurdum

Relation between Proof by Contradiction and Proof by Contraposition

- Proof by contraposition can only be used for statements that are universal and conditional. - Any statement that can be proved by contraposition can also be proved by contradiction. But the converse is not true. - Proof by contradiction also works for other types of statements. Statements such as "√2 is irrational" can be proved by contradiction but not by contraposition.