Title: True Lies
Speaker: Prof. Thomas Ågotnes (University of Bergen)
Date & Time: 10 December 2014 (Wednesday), 14:00-16:00
Place: Seminar room 259, Main Teaching Building, Xixi campus, Zhejiang University

Abstract: A lie is a statement that is false, or at least believed to be false, when it is announced. But the world after the lie is not the same as the world before the lie, so is the statement necessarily still false after the lie is announced – is the lie still a lie? This talk is about true lies. These are “self-fulfilling” lies that become true when they are made. The analysis is based on formal modal epistemic logic. True lies are conceptually related to Moore sentences, sentences that are true but become false when they are announced, but the exact relationship between the two types of sentences is not trivial. I will also discuss impossible lies (lies that stay false when announced) as well as the relationships to successful formulas (truths that stay truths when announced) and self-refuting truths (truths that become false when announced). The talk is based on joint work with Hans van Ditmarsch and Yanjing Wang.

Lecture slides: Download (7.63 MB)