 The historical roots of argumentation research in artificial intelligence can be traced back to work on non-monotonic logics (see entry on  non-monotonic logics)  and defeasible reasoning (see entry on  defeasible reasoning).  Since then, three main different perspectives have emerged (Eemeren, Garssen, et al. 2014: ch. 11): the theoretical systems perspective, where the focus is on theoretical and formal models of argumentation (following the tradition of philosophical and formal logic); the artificial systems perspective, where the aim is to build computer programs that model or support argumentative tasks, for instance, in online dialogue games or in expert systems; the natural systems perspective, which investigates argumentation in its natural form with the help of computational tools (e.g., argumentation mining [Peldszus &amp; Stede 2013; Habernal &amp; Gurevych 2017], where computational methods are used to identify argumentative structures in large corpora of texts).