The 2007 Annual Conference of the Australasian Association for Logic

s of contributed talks CONRAD ASMUS, Paraconsistency on the rocks. Philosophy, University of Melbourne, Victoria 3010, Australia. E-mail: cmasmus@unimelb.edu.au. Can commitment to a theory of inference overflow into commitment to non-inferential theories? Specifically, does a commitment to paraconsistency (the view that the inference from a contradiction to any sentence is invalid) commit one to true contradictions? While there is no immediate reason to think so, I will show that, once we take into account the philosophy of validity, paraconsistency drives one onto the rocks of Dialetheism. PHILLIPPE BALBIANI, ALEXANDRU BALTAG, HANS VAN DITMARSCH, ANDREAS HERZIG, TOMOHIRO HOSHI AND TIAGO DE LIMA, Arbitrary announcement logic. Department of Computer Science, University of Otago, PO Box 56, Dunedin 9054, New Zealand, and IRIT, Université Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse, Cedex 9, France. E-mail: hans@cs.otago.ac.nz. Public announcement logic is an extension of multi-agent epistemic logic with dynamic operators to model the informational consequences of announcements to the entire group of agents. We propose an extension of public announcement logic, called arbitrary announcement logic, with a dynamic modal operator that expresses what is true after arbitrary announcements. Intuitively, φ expresses that φ is true after an arbitrary announcement . For an example, let us work our way upwards from a concrete announcement. When c © 2008, Association for Symbolic Logic 1079-8986/08/1403-0009/$1.60