alethic

Alethic is an adjective meaning relating to truth or the nature of truth. The term comes from the Greek aletheia, often glossed as unconcealedness or truth, built from a- (not) and lethe (concealment). In philosophy, alethic is used to describe properties, modalities, and investigations that concern truth as such, rather than belief, justification, or obligation.

Alethic modality concerns how truth occurs across possible worlds. Concepts such as alethic necessity and alethic possibility designate, respectively, what must be true and what could be true in every possible world. This usage is common in modal logic and semantics, where truth conditions are central. Alethic logic treats truth as a primary modality distinct from epistemic or deontic modalities.

Historically, discussions of truth and its modality have involved alethic considerations from ancient to contemporary philosophy, including theories of truth, correspondence, and constraint-based semantics. In modern formal contexts, alethic ideas are encoded in logics with operators that reflect necessity, possibility, and impossibility across models or worlds. Outside philosophy, alethic is rare but appears in scholarly discussions about truth conditions in language and theory.

See also: aletheia; truth conditions; modal logic; alethic necessity; possible-world semantics.