# Category:Reductio ad Absurdum

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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 $\neg \phi$.

## Pages in category "Reductio ad Absurdum"

The following 13 pages are in this category, out of 13 total.

### R

- Reductio ad Absurdum
- Reductio ad Absurdum for Hilbert Proof System Instance 1 for Predicate Logic
- Reductio ad Absurdum/Explanation
- Reductio ad Absurdum/Proof Rule
- Reductio ad Absurdum/Proof Rule/Tableau Form
- Reductio ad Absurdum/Sequent Form
- Reductio ad Absurdum/Variant 1
- Reductio ad Absurdum/Variant 1/Proof 1
- Reductio ad Absurdum/Variant 1/Proof by Truth Table
- Reductio ad Absurdum/Variant 2
- Reductio ad Absurdum/Variant 2/Proof 1
- Reductio ad Absurdum/Variant 2/Proof by Truth Table