 An important question in situation semantics is how exactly situations enter the semantic interpretation process. Are they articulated via syntactically represented variables, or are they “unarticulated constituents” (Perry 1986, Récanati 2002), possibly mere indices of evaluation? The issue is well explored for times and possible worlds (see the entry on   ontological commitment).  Kripke’s semantics for modal logic allows quantification over possible worlds only in the metalanguage (see the entry  modal logic),  for example. Likewise, in Prior’s tense logic (see the entry  Arthur Prior),  quantification over times is confined to the metalanguage (see the entry  time).