In the late 1990s, AI witnessed an increasing use of the term 'argumentation' within its bounds: in natural language processing, in user interface design, in logic programming and nonmonotonic reasoning, in Al's interface with the legal community, and in the newly emerging field of multi-agent systems. It seemed to me that many of these uses of argumentation were inspired by (often inspired) guesswork, and that a great majority of the AI community were unaware that there was a maturing, rich field of research in Argumentation Theory (and Critical Thinking and Informal Logic) that had been steadily re­ building a scholarly approach to the area over the previous twenty years or so. Argumentation Theory, on its side; was developing theories and approaches that many in the field felt could have a role more widely in research and soci­ ety, but were for the most part unaware that AI was one of the best candidates for such application.