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In logic and mathematics, a logical value, also called a truth value, is a value indicating to what extent a proposition is true.
In classical logic, the only possible truth values are true and false. However, other values are possible in other logics: fuzzy logic and other forms of multi-valued logic 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.
See also
External links
- Weblog entry "How many is two?" by Andrej Bauer discussing the relationship between truth values in intuitionistic logic and topos theory on the one hand and classical logic on the other.
"Logical value"