more from Michèle Friend

### Single Idea 3678

#### [catalogued under 2. Reason / E. Argument / 5. Reductio ad Absurdum]

Full Idea

Reductio ad absurdum arguments are ones that start by denying what one wants to prove. We then prove a contradiction from this 'denied' idea and more reasonable ideas in one's theory, showing that we were wrong in denying what we wanted to prove.

Gist of Idea

Reductio ad absurdum proves an idea by showing that its denial produces contradiction

Source

Michèle Friend (Introducing the Philosophy of Mathematics [2007], 2.3)

Book Reference

Friend,Michèle: 'Introducing the Philosophy of Mathematics' [Acumen 2007], p.34

A Reaction

This is a mathematical definition, which rests on logical contradiction, but in ordinary life (and philosophy) it would be enough to show that denial led to absurdity, rather than actual contradiction.