nLab ex falso quodlibet

Context

Foundations

foundations

The basis of it all

 Set theory

set theory

Foundational axioms

foundational axioms

Removing axioms

Contents

Idea

Ex falso quodlibet is Latin for “from falsehood, anything”. It is also called the principle of explosion.

In logic it refers to the principle that when a contradiction can be derived in a logical system, then any proposition follows.

In type theory it is the elimination rule of the empty type (see there).

Ex falso quodlibet holds in many systems of logic, such as classical logic and intuitionistic logic, but it fails to hold in paraconsistent logic, which was devised to allow controlled inconsistency.

Variants of the principle’s name include ex falso sequitur quodlibet, “from falsehood, anything follows”, and ex contradictione (sequitur) quodlibet, “from contradiction, anything (follows)”).

References

Last revised on August 16, 2024 at 17:28:05. See the history of this page for a list of all contributions to it.