The notions of defeasibility and defeasible reasoning have generated a great deal of interest in various research communities. Here I want to focus on their use in logic and argumentation studies. I will approach these topics from the perspective of an informal logician who finds himself struggling with some issues that surround the idea of and the deployment of the concept of defeasibility. My intention is to make those struggles as clear as I can.

Design deliberation refers to the process of thoughtfully weighing options, before making a design decision. This process is strongly related to argumentation, not only because of the well-known relation between argumentation and deliberation, but also due to characteristics of the design process. However, no structural model of team design deliberation exists to guide designers’ practice. This paper checks the hypothesis of inter-dependence between argument structures and group decision-making struc-ture as expressed through prescribed deliberation stages.

In this paper, I critically examine the main accounts of goals in argumentative discourse, aiming to formulate an account that is suitable for the examination of public political arguments, where typically multiple legitimate goals are pursued simultaneously. Such arguments are viewed as contributions to what can be dialectically reconstructed as multiple simultaneous discussions, and are analysed as strategic manoeuvres that can under certain conditions be reasonable but may, if such conditions are violated, become fallacious.