Deontic Ambiguities in Legal Reasoning

Abstract

What happens if the way in which we handle a genuine deontic conflict —i.e., a deontic ambiguity— matters regarding the application of other norms that are not directly affected by that conflict? We argue that the law requires sometimes propagating the ambiguity to other norms and sometimes confining it to some norms only. We explore this issue and model different reasoning patterns. The problem is addressed in a new variant of Defeasible Deontic Logic. The contribution of this paper is threefold: (a) we extend the treatment of ambiguity blocking and propagation to Defeasible Deontic Logic; (b) we discuss reasoning patterns in the law, especially in criminal law, where we need to deal with both ambiguity blocking and ambiguity propagation in the same legal system and logic; (c) we devise an annotated variant of Defeasible Deontic Logic where we distinguish literals that must be obtained through an ambiguity-blocking mechanism from those that are derived using an ambiguity-propagating mechanism.