Full Idea
Theoretical entities (which is everything, according to Quine) are postulated by us in a threefold fashion as an object (1) to which we refer, (2) of which we predicate, and (3) over which we quantify.
Gist of Idea
For Quine everything exists theoretically, as reference, predication and quantification
Source
report of Willard Quine (works [1961]) by José A. Benardete - Metaphysics: the logical approach Ch.12
Book Reference
Benardete,José A.: 'Metaphysics: The Logical Approach' [OUP 1989], p.87
A Reaction
Postulating and referring seem to be the same thing. Quantifying makes each entity a perfectly individuated object in a domain. Logicians then panic about vagueness. They should also panic about overlap.