While the term "proposition" may sometimes be used in everyday language to refer to a linguistic statement which can be either true or false, the technical philosophical term, which differs from the mathematical usage, refers exclusively to the non-linguistic meaning behind the statement. The term is often used very broadly and can also refer to various related concepts, both in the history of philosophy and in contemporary analytic philosophy. It can generally be used to refer to some or all of the following: The primary bearers of truth values (such as "true" and "false"); the objects of belief and other propositional attitudes (i.e. what is believed, doubted, etc.); the referents of "that"-clauses (e.g. "It is true "that the sky is blue"" and "I believe "that the sky is blue"" both involve the proposition "the sky is blue"); and the meanings of declarative sentences.