TENSES Ii K REAL TIME by J. v -4 ~ BENTHEM in Groningen (Netherla.nds)')
1, Linguistic approaches to tense
Xatural language has a systematic mechanism for describing events in a temporal perspective: so-called "tenses" indicate whether the event is past, present or future. And even more complex indications are possible, as exemplified in "Lucas had laughed" (a past perfect), "Lucas will have laughed" (a future perfect) -both involving some kind of iteration of simple tenses -or "Lucas is laughing" (a present progressive) -expressing a different kind of present tense. Not all languages have the same tense system, but there is enough global regularity to warrant a logical investigation of the phenomenon, known under the name of "tense logic".
Traditionally, tense-logical languages analyze tenses as operators on propositions. The paradigmatic example is the system of PRIOR, with operators * ) 1 would like to thank the Dep:irtment of hhthematics, Simon Frnsor University, Rnrnahy (B.C.), Canada, for its hospitality during the fall term of 1983-when tShk paper appeared as it research report (83-28). In particular, I enjoyed many stimulating discussions with STEVE THOMASON on this subject.