Defeasible Deontic Logic: Arguing about Permission and Obligation

Defeasible deontic logic uses techniques from non-monotonic logic to address various challenges in normative reasoning, such as prima facie permissions and obligations, moral dilemmas, deontic detachment, contrary-to-duty reasoning and legal interpretation. In this article, we use formal argumentation to design defeasible deontic logics, based on two classical deontic logics. In particular, we use the ASPIC+ structured argumentation theory to define non-monotonic variants of well-understood monotonic modal logics. We illustrate the ASPIC+-based approach and the resulting defeasible deontic logics using argumentation about strong permission.