User:Astreven/sandbox

William of Soissons lived in Paris in the 12th century. Hij is known as the first one to proof ex contradictione quod libet, or that from a contradiction every assertion may be inferred as true,. Later Clarence Irving Lewis formalized this proof as follows :

Proof [bewerken]

A &¬ A : beïng a contradiction.

B : beïng any possible assertion.

(1) A &¬ A → A (2) A → A∨B (3) A &¬ A → A∨B (4) A &¬ A → ¬A (5) A &¬ A → (A∨B) &¬A (6) (A∨B) &¬A → B (7) A &¬ A → B

Sources