The System K t of Minimal Tense Logic

We come now to the problem of devising a “tense logic” — that is, a set of rules governing the mutual logical interrelationships of the tense operators as defined within the framework of a (R/U)-calculus. Let us begin here with the question of an irreducibly basic or minimal tense logic; “minimal” in the sense of involving no assumptions whatsoever regarding the nature of the U-relation. This last condition is imposed to assure “minimality” in the sense of topological neutrality — i. e., the lack of any specific assumptions about the structure of time.