…the term existence is properly a term, not of logic, but of metaphysics; and metaphysically understood, an object exists, if and only if, it reacts with every other existing object of the same universe. But in the definition of a logical proper name, exist is used in its logical sense, and means merely to be a singular of a logical universe, or universe of discourse.
http://www.commens.org/dictionary/entry/quote-basis-pragmaticism-29