John Searle proposed a model of speech acts that categorizes utterances based on their illocutionary force, or purpose. This model includes five types of speech acts: assertives, which express a belief or a fact; directives, which attempt to get the listener to do something; commissives, which commit the speaker to a future action; expressives, which express the speaker's attitude or emotion; and declaratives, which change the status or the reality of something. For example, asserting can be used to state or report facts, directing can be used to ask or order someone to do something, commissives can be used to promise or agree to do something, expressives can be used to thank or apologize, and declaratives can be used to name or declare something.