Category:Reductio ad Absurdum

From ProofWiki
Jump to navigation Jump to search

This category contains pages concerning Reductio ad Absurdum:

Reductio ad absurdum is a valid argument in certain types of logic dealing with negation $\neg$ and contradiction $\bot$.

This includes classical propositional logic and predicate logic, and in particular natural deduction, but for example not intuitionistic propositional logic.

Proof Rule

If, by making an assumption $\neg \phi$, we can infer a contradiction as a consequence, then we may infer $\phi$.
The conclusion $\phi$ does not depend upon the assumption $\neg \phi$.