Absurdum, REDUCTIO AD, a method of proving a truth indirectly, by showing that to suppose the proposition untrue would lead to an absurdity, or that the contrary of the proposition is impossible. The method is much used in geometry.
Absurdum, REDUCTIO AD
Chambers's Encyclopaedia, Volume 1: A to Beaufort, p. 21
Source scan(s): p. 0034