地点: 文史楼215
时间: 10月20日下午
第一场：15:10-16:00
Epistemic Games: Public Announcements and Questions-and-Answers
Prof. dr. Thomas ?gotnes
Department of Information Science and Media Studies, University of Bergen, Norway
Dynamic epistemic logic describes the possible information-changing actions available to individual agents, and their knowledge pre- and post conditions. For example, public announcement logic describes actions in the form of public, truthful announcements. However, little research so far has considered describing and analysing rational choice between such actions, i.e., predicting what rational self-interested agents actually will or should do. Since the outcome of information exchange ultimately depends on the actions chosen by all the agents in the system, and assuming that agents have preferences over such outcomes, this is a game theoretic scenario. This is an interesting general research direction, combining logic and game theory in the study of rational information exchange. In the talk I will, in particular, focus on two particular cases in detail. First, I consider the case where available actions are public announcements, and where each agent has a (typically epistemic) goal formula that she would like to become true. What will each agent announce? The truth of the goal formula also depends on the announcements made by other agents, thus we have a game-theoretic scenario. I discuss how such *public announcement games* can be analysed. Second, I consider the similar setting where instead of choosing an announcement each player chooses a question the other player is obliged to truthfully answer. What are the best questions to ask? Again, this question can be discussed by analysing the resulting *question-answer games*. The talk is based on joint work with Johan van Benthem, Hans van Ditmarsch and Stefan Minica.
第二场：16:30-18:00
The Inquisitive Turn: a new perspective on semantics, logic, and pragmatics
Dr. Floris Roelofsen
University of Amsterdam
The aim of inquisitive semantics is to develop a new notion of semantic meaning that captures both informative and inquisitive content. This enriched notion of meaning is intended to provide a new foundation for the analysis of one of the primary usages of language, namely the exchange of information.
In inquisitive semantics, a sentence is taken to express a proposal to update the common ground of a conversation in one or more ways. If a sentence proposes two or more alternative updates it is inquisitive, inviting a response from other participants that establishes at least one of the alternative updates.
Formally, the proposition expressed by a sentence is a set of possibilities. Each of these possibilities in turn is a set of possible worlds, embodying a potential update of the common ground. Purely informative sentences express a proposition containing just one alternative possibility. Inquisitive sentences express a proposition containing two or more alternative possibilities.
The way in which inquisitive semantics enriches the notion of meaning changes our perspective on logic as well. Besides the classical notion of en- tailment, the semantics also gives rise to a new notion of inquisitive entailment, and to a new logical notion of relatedness, which determines whether one sen- tence compliantly addresses or resolves the issue raised by another.
The way in which inquisitive semantics enriches the notion of meaning also changes our perspective on pragmatics. The main objective of pragmatics is to explain aspects of interpretation that are not directly dictated by semantic con- tent, in terms of general features of rational human behaviour. Since inquisitive semantics changes the notion of semantic content, pragmatics changes with it.
Gricean pragmatics consists exclusively of speaker-oriented rules for provid- ing information. Inquisitive pragmatics has the same basic objective, but is more general: it is both speaker- and hearer-oriented, and specifies rules for exchanging information rather than just providing information. This makes it possible to derive a wider range of implicatures, in particular those that arise from inquisitiveness. Furthermore, the new logical notion of relatedness allows for a more explicit treatment of quantity implicatures. In particular, it makes it possible to state in a principled way what the alternatives are that a given proposition should be compared with in order to derive quantity implicatures.