Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!ihnp4!zehntel!hplabs!sri-unix!CLT@SU-AI.ARPA From: CLT@SU-AI.ARPA Newsgroups: net.ai Subject: Incompleteness in Modal Logic Message-ID: <17415@sri-arpa.UUCP> Date: Fri, 9-Mar-84 04:34:00 EST Article-I.D.: sri-arpa.17415 Posted: Fri Mar 9 04:34:00 1984 Date-Received: Tue, 13-Mar-84 07:56:49 EST Lines: 29 From: Carolyn Talcott[Forwarded from the CSLI bboard by Laws@SRI-AI.] Subject: SEMINAR IN LOGIC AND FOUNDATIONS OF MATHEMATICS SPEAKER: Johan van Benthem, University of Groningen TITLE: "From Completeness Results to Incompleteness Results in Modal Logic" TIME: Wednesday, Mar. 14, 4:15-5:30 PM PLACE: Stanford Mathematics Dept. Room 383-N For a long time the main activity in intensional logic consisted in proving completeness theorems, matching some logic with some modal class. In the early seventies, however, various incompleteness phenomena were discovered - e.g. such a match is not always possible. By now, we know that the latter phenomenon is the rule rather than the exception, and the issue of the `semantic power' of the possible worlds approach has become a rather complex and intriguing one. In this talk I will give a survey of the main trends in the above area, concluding with some open questions and partial answers. In particular, a new type of incompleteness theorem will be presented, showing that a certain tense logic defies semantic modelling even when both modal class and truth definition are allowed to vary.