Highlights in the Development of Tense-Logic

In 1954, on the 27^th August, Arthur Norman Prior presented his ideas of tense-logic¹ for the first time. He developed the field further in many publications until his death in 1969. His books Time and Modality (1957a), Past, Present and Future (1967), and Papers on Time and Tense (1968) were clearly vital milestones. Much of Prior's personal motivation had to do with his struggle with the logical tension between the theological doctrines of divine foreknowledge and human freedom. It turned out that tense-logic gave rise to a powerful tool for dealing with this and similar problems. Furthermore, important highlights in Prior's tense-logic were the development of branching time and the introduction of instant propositions (leading to what has later been called 'hybrid logic'). Since Prior's death, many further developments of formal tense-logic and its semantics have been presented and carefully investigated. In philosophical logic, many researchers have focused on discussions regarding 'the true future' and the notion of 'the thin red line'.