Situation Semantics

chapter for the volume Introduction to the Philosophy of John Perry, ed. by Raphael van Riel and Albert NewenInternational audienceThis paper is an occasion to go back to Jon Barwise and John Perry's Situations and Attitudes (1983). The aim is to bring to the foreground the main tenets of situation semantics, and to give the reader with a fair sense of the theoretical motivations that were driving the framework, and that continue to be of major significance to Perry's larger philosophical enterprise. I start by rehearsing some of the central aspects of what can be described as the Fregean heritage, which is important in order to understand the context in which situation semantics saw light, and to appreciate the almost revolutionary nature of some of the ideas behind it. After having clarified the background, I turn to one of the main motivations behind situation semantics: the search for an account of meaning that relies upon an account of information, where the latter is crucially driven by the task of explaining how cognitive agents like us are led to act in ways they do, given how they are attuned to their environment

Common Knowledge: A Survey

This paper discusses the motivation behind common knowledge. Common knowledge has been argued to be necessary for joint action in general and for language use as a particular kind of joint action. However, this term has been broadly interpreted. Two major issues must be addressed: (1) What mental state corresponds to common knowledge, i.e., is knowledge, belief or supposition the appropriate mental attitude? (2) What inference process allows agents to achieve common knowledge? Most generally, common knowledge is used to describe the knowledge that is evidenced in reflexive reasoning. The term has also been used to refer to facts or objects which are mutually salient. One of the main problems for a theory of common knowledge is whether knowledge is the appropriate mental attitude. It seems as though probabilistic beliefs might approximate the cognitive phenomenon of common knowledge more closely than knowledge. The main problem with a usable notion of common knowledge is that inference must play a critical role in what becomes common knowledge. I discuss the nature of conversational inference. It has a number of properties that distinguish it from other inferential systems, such as being apparently abductive and probabilistic, but a precise characterization of it is an unsolved problem. I suggest that in cases where ensuring common knowledge really matters, participants in dialogue accomplish this is by exploiting opportunities for redundancy in conversation