The Propositional attitude reference article from the English Wikipedia on 24-Apr-2004
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Propositional attitude

A propositional attitude is a relational mental state connecting a person to a proposition. They are often assumed to be the simplest components of thought and can express meanings or content that can be true or false. In being a type of attitude they imply a person can have different mental postures towards a proposition, for example, believing, desiring or hoping and therefore imply intentionality.

Linguistically, they are denoted by an embedded "that" clause, for example, 'Sally believed that she had won'.

See also