 In keeping with this proposal, a common assumption (Heim 1982; Kamp 1981; Kamp and Reyle 1993; Diesing 1992; Kratzer 1995; and many others) is that indefinites such as bare plurals and indefinite singulars contribute predicates with unbound variables to the logical forms containing them. In the course of syntactic operations, the material in the sentence is divided up into the restrictor and scope (e.g., Diesing 1992). If the sentence contains a quantificational adverb (e.g., “usually”, “always”), then any unbound variables in the restrictor are bound by that quantificational adverb, as in example  (28)  above. However, if there is no quantificational adverb, the generic operator Gen is introduced to bind those variables. Thus, to take a simple example, the logical form of a sentence like “ravens are black” may be given as follows: