asserter

An asserter is a person or entity that makes an assertion—presenting a proposition as true. In everyday use, the asserter is the speaker or writer who puts forward a claim as fact.

In philosophy and linguistics, the concept of the asserter is tied to theories of assertion and speech acts. An assertion is a speech act that commits the speaker to the truth of its content; the asserter is identified with the source of the proposition and bears responsibility for its justification and credibility. Analyses often examine how the asserter’s identity, stance, or authority affects the reception and truth conditions of the asserted content.

In formal logic and semantics, the term denotes the agent associated with a proposition’s claim. Some discussions distinguish the content of the assertion from the speaker, focusing on how attribution of assertion relates to belief, knowledge, or credibility.

In computer science and software testing, assertion mechanisms enable runtime checks. An asserter in this context may refer to the code element that evaluates a condition and signals a failure when it is not met, or to a testing utility that provides fluent interfaces for expressing and reporting failed expectations.

Related terms include assertion and the verb to assert. The spelling asserter is one of several attestations of the noun for one who asserts; some sources also use assertor as a variant.