Lecturer: Patrick Blackburn

Arthur Prior (1914–1969) is best known as the inventor of tense logic, but in the last few years of his life, his work took an unexpected turn: he realized that the powerful new forms of modal logic he had invented for talking about time could be used for talking about pretty much anything. Nowadays, this is old news: we are used to description logic and Amsterdam-style modal logic, which emphasize the links between modal and classical logic, but it was a novelty in Prior’s day. In this course, I will describe the path that led him to this insight and the tools he invented (or re-invented) along the way, such as nominals, propositional quantification, and the universal modality.

This course will be a blend of technical developments (mostly centered on Henkin-style modal constructions for enriched modal logics) and historical and philosophical background and motivation. I will use contemporary modal notation and concepts for the technical developments but will occasionally use older Prior-style notation (such as the UT calculus) when making historical or philosophical points.