{"id":5558,"date":"2026-02-02T13:13:49","date_gmt":"2026-02-02T12:13:49","guid":{"rendered":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/?p=5558"},"modified":"2026-03-20T17:43:32","modified_gmt":"2026-03-20T16:43:32","slug":"lira-session-johan-van-benthem-6","status":"publish","type":"post","link":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/2026\/02\/lira-session-johan-van-benthem-6\/","title":{"rendered":"LIRa session: Johan van Benthem"},"content":{"rendered":"<p>The\u00a0<a href=\"https:\/\/video.uva.nl\/media\/LIRa+seminar+on+2026-03-19+by+Johan+van+Benthem\/0_d47vdkms\">recording of this talk is available here<\/a>.<\/p>\n<p>Speaker: <a href=\"https:\/\/staff.fnwi.uva.nl\/j.vanbenthem\/\">Johan van Benthem<\/a> (ILLC, University of Amsterdam &amp; Department of Philosophy, Stanford University &amp; Department of Philosophy, Tsinghua University)<\/p>\n<p>Date and Time: Thursday, March&nbsp;19th 2026, 16:30-18:00<\/p>\n<p>Venue: ILLC Seminar Room F1.15, Science Park 107 <strong>and<\/strong>\u00a0<a href=\"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/guidelines-for-online-sessions\/\">online<\/a>.<\/p>\n<p>Title: <strong>Incompleteness for modal logics: What is at stake?<\/strong><\/p>\n<p><em>Abstract.<\/em> Incompleteness of several modal logics was discovered in the 1970s, signalling a mismatch between what is valid in their relational frame semantics and what can be proved by the basic deductive engine of the logic.<br \/>\nI will explain the phenomenon, and sketch a research program of analyzing semantic arguments in terms of the proof strength they require. Next I will raise some broader issues such as the connection\/tension between semantics and proof theory in logic, and what is the real content of completeness theorems.<br \/>\nIn doing so, my purpose is twofold: explain interesting technicalities and trigger some philosophical discussion.<br \/>\nYou may think the risks of incompleteness occur far away from the area of agent logics or DEL. But I will present one recent candidate for incompleteness which is relatively close to the LIRa world.<\/p>\n<p>Reference: J. van Benthem, \u2018Incompleteness, semantics and proof systems in modal logic\u2019, <em>Theoria<\/em>, to appear.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The\u00a0recording of this talk is available here.<br \/>\nSpeaker: Johan van Benthem (ILLC, University of Amsterdam &amp; Department of Philosophy, Stanford University &amp; Department of Philosophy, Tsinghua University)<br \/>\nDate and Time: Thursday, March&nbsp;19th 2026, 16:30-18:00<br \/>\nVenue: ILLC Seminar Room F1.15, Science Park 107 and\u00a0online.<br \/>\nTitle: Incompleteness for modal logics: What is at stake?<br \/>\nAbstract. Incompleteness of several modal logics was discovered [&#8230;]<\/p>\n","protected":false},"author":11,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[14],"tags":[],"class_list":["post-5558","post","type-post","status-publish","format-standard","hentry","category-all"],"_links":{"self":[{"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/posts\/5558","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/users\/11"}],"replies":[{"embeddable":true,"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/comments?post=5558"}],"version-history":[{"count":8,"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/posts\/5558\/revisions"}],"predecessor-version":[{"id":5603,"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/posts\/5558\/revisions\/5603"}],"wp:attachment":[{"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/media?parent=5558"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/categories?post=5558"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/projects.illc.uva.nl\/lgc\/seminar\/wp-json\/wp\/v2\/tags?post=5558"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}