The claim that formal semantics analyzes predicative adjectives as functions from individuals to truth values states a foundational definition in linguistics and philosophy, requiring no citation.
The claim outlines a standard textbook definition in formal semantics (Montague semantics), where property-denoting expressions like predicative adjectives are modeled as functions mapping individuals (type e) to truth values (type t). This is a definitional truism within the discipline of semantics, making it common knowledge for the field.