If the (monadic[23])  second-order quantifiers are interpreted as plural quantifiers, as recommended by Boolos (1984), then, arguably, they carry no additional ontological commitments beyond those already carried by the first-order quantifiers. Plural quantification is ontologically innocent according to Boolos: to refer to some things plurally—some books, for example—is not to refer to a plural entity—a set, or set-like entity, with books as members—but to refer to the things—the books themselves—in an irreducibly plural way. [24]  Individual and plural quantifiers range over the same domain. Since quantifier criteria attribute ontological commitment based on the domain of quantification, they reveal no hidden ontological cost to theories couched in an extension of first-order logic that includes plural quantification.  To get this result, we simply extend quantifier criteria to apply to plural as well as individual variables. In slogan form: “to be is to be the value of some variable or the values of some variables” (Boolos 1984). A plural variable takes as its semantic value a plurality of entities, not a plural entity (such as a set or class). Plural entities are not needed to serve as semantic values—not, in any case, if the language in which the semantics is done is itself a plural language.