Common knowledge in argumentation

We argue that common knowledge, of the kind used in reasoning in law and computing is best analyzed using a dialogue model of argumentation (Walton Krabbe 1995). In this model, implicit premises resting on common knowl-edge are analyzed as endoxa or widely accepted opinions and generalizations (Tardini 2005). We argue that, in this sense, common knowledge is not really knowledge of the kind represent by belief and/or knowledge of the epistemic kind studied in current epistemology. This paper takes a different approach, defining it in relation to a common commitment store of two participants in a rule-governed dialogue in which two parties engage in rational argumentation (Jackson Jacobs 1980; van Eemeren Grootendorst 2004). A theme of the paper is how arguments containing common knowledge premises can be stud-ied with the help of argumentation schemes for arguments from generally accepted opinion and expert opinion. It is argued that common knowledge is a species of provisional acceptance of a premise that is not in dispute at a given point in a dialogue, but may later be defeated as the discussion proceeds.