One proposed restriction confines rational figurative predication to declarative reports (الإسناد الخبري), since statements affirm or deny a relation and can be judged true or false.
The book examines this restriction and explains that a predicate can be assigned to a nonproper bearer in nondeclarative forms (الإنشاء) as well—commands, prohibitions, and expressions of wish.
Commands and wishes are not themselves true or false in the way propositions are; nevertheless, their internal predicational relation can still be analyzed rhetorically.