Deontic Redundancy: A Fundamental Challenge for Deontic Logic

To decide which norms can be removed from a system, we need to know when a norm is redundant. After shifting the focus of attention in deontic logic from detachment of obligations and permissions to deontic redundancy, I discuss in this paper five benchmark examples of deontic redundancy in reasoning about permissions, intermediate concepts and constitutive norms, deontic dilemmas, temporal deontic reasoning and contrary-to-duty reasoning. Then I discuss those benchmark examples in four formal approaches to deontic reasoning: traditional model logic, dynamic approaches, violation oriented or diagnostic systems, and imperativist or norm based approaches.