 Many of the questions concerning the interrelation of existence and quantification arising here correspond to well known problems in modal first-order logics, where an extensive discussion on these issues started already with Frege and Russell and peaked in the 1940s-1950s in the works of R. Barcan-Marcus, R. Carnap, W. Quine, R. Montague, and others (see the entry on  modal logic).  A central issue in first-order modal logics relates to the validity or invalidity of the so-called Barcan formula, a temporal version of which intuitively says: “If at some time in the future there will be something that is \(Q\), then there is something now that will be \(Q\) at some time in the future.” Whether this statement is guaranteed to be true crucially depends on how the local domains at the various instants in time are construed and what our quantifiers range over. What is more, temporal logic yields two versions of the Barcan formula, one for the future and one for the past.