A Study of Argumentative Characterisations of Preferred Subtheories

Classical logic argumentation (Cl-Arg) under the stable semantics yields argumentative characterisa- tions of non-monotonic inference in Preferred Sub- theories. This paper studies these characterisations under both the standard approach to Cl-Arg, and a recent dialectical approach that is provably rational under resource bounds. Two key contributions are made. Firstly, the preferred extensions are shown to coincide with the stable extensions. This means that algorithms and proof theories for the admissible semantics can now be used to decide credulous inference in Preferred Subtheories. Secondly, we show that as compared with the standard approach, the grounded semantics applied to the dialectical approach more closely approximates sceptical inference in Preferred Subtheories.