Postscript (on interpersonal discussion)

Reasoning and argument sometimes occur in back-and-forth argumentative discussions. The goal of participants in an argumentative discussion is to reach a shared rationally supported position on an issue. The discussion is a persuasion dialogue if it starts with a proponent advancing a thesis, but an inquiry or deliberation dialogues if it starts with a factual or policy issue. Other pure types of dialogue (information-seeking, negotiation, quarrel) are not argumentative discussions. Formal systems for conducting argumentative discussions are more constrained than real-life discussions, and are difficult to assess for soundness and completeness if they are realistic enough to allow for data-gathering and modification of theses. But their development has both theoretical and practical benefits. In particular, there may be a place for formal systems of inquiry dialogue where interlocutors arrive jointly at an answer to a question that none of them can reach individually.