In logic, a truth value, or truth-value, is a value indicating to what extent a statement is true.
In classical logic, the only possible truth values are true and false.
However, other values are possible in other logics.
A simple intuitionistic logic has truth values of true, false, and unknown; fuzzy logic and other forms of multi-valued logic also use more truth values than simply true and false.
Algebraically, the set {true,false} forms a simple Boolean algebra.
Other Boolean algebras may be used as sets of truth values in multi-valued logic, while intuitionistic logic generalises Boolean algebras to Heyting algebras.
In topos theory, the subobject classifier of a topos takes the place of the set of truth values.
This nomenclature is perhaps more consonant with usages that prevail in mathematics than with those of philosophy.
