Nontruthfunctional

Nontruthfunctional is a term used in logic and the philosophy of language to describe expressions whose truth-conditions cannot be determined solely from the truth-values of their component propositions. In a truth-functional system, the value of a complex sentence is a function of the values of its parts. Nontruthfunctional items resist that kind of compositional analysis, requiring additional information such as context, speaker, world, or mental state.

The concept is often invoked to account for natural-language phenomena where context or perspective affects meaning. Indexicals and demonstratives—words like now, here, I, this, and that—are classic examples: the truth of a sentence containing such terms depends on who is speaking, when, and where it is uttered. Similarly, proper names or definite descriptions can shift reference with context, altering truth conditions in ways not captured by a purely truth-conditional account. Intensional contexts, such as sentences involving beliefs, desires, or obligations, also exhibit nontruthfunctional behavior, since what is true can vary with an agent’s information or perspective across possible worlds.

Recognizing nontruthfunctional elements encourages alternative semantic frameworks, including contextualist and possible-world theories, which allow truth conditions to depend on factors beyond simple propositional content. The distinction between truth-functional and nontruthfunctional expressions helps clarify debates in semantics, philosophy of language, and formal logic about how meaning is composed and how context influences interpretation.

See also: truth-functional logic, intensional logic, indexicals, context-dependence.