 (7) and (8) are called belief ascriptions, for the obvious reason that they ascribe a belief to a subject. Belief ascriptions are one sort of propositional attitude ascription—other types include ascriptions of knowledge, desire, or judgment. As will become clear in what follows, propositional attitude ascriptions have been very important in recent debates in semantics. One of the reasons why they have been important is exemplified by (7) and (8). Because these sentences can differ in truth-value despite the fact that they differ only with respect to the italic words, and these words both share a reference and occupy the same place in the structure of the two sentences, we say that (7) and (8) contain a non-extensional context: roughly, a “location” in the sentence which is such that substitution of terms which share a reference in that location can change truth-value. (They’re called “non-extensional contexts” because “extension” is another term for “reference”.)