 Pursuing this kind of analysis, one is very quickly confronted with two intricate problems. First, how should one treat declarative sentences? Should one perhaps separate them into a specific linguistic category distinct from the ones of names and function symbols? And second, how—from a functional point of view—should one deal with predicate expressions such as ‘is a city’, ‘is tall’, ‘runs’, ‘is bigger than’, ‘loves’, etc., which are used to denote classes of objects, properties of objects, or relations between them and which can be combined with (applied to) singular terms to obtain sentences? If one considers predicates to be a kind of functional expressions, what sort of names are generated by applying predicates to their arguments, and what can serve as referents of these names, respectively values of these functions?