Contrary-to-Duty Paradoxes and Counterfactual Deontic Logic

Henry Prakken and Marek Sergot Dyadic Deontic Logic and Contrary-to-duty Obligations

One of the main issues in the discussion on standard deontic logic (SDL) is the representation of contrary-to-duty (CTD) obligations. A well-known example is Forrester’s (1984) paradox of the gentle murderer: it is forbidden to kill, but if one kills, one ought to kill gently. Intuitively, one would feel that these sentences are consistent, but in SDL no (obvious) consistent formalisation is av...

On How Kelsenian Jurisprudence and Intuitionistic Logic help to avoid Contrary-to-Duty paradoxes in Legal Ontologies

In this article we show how Hans Kelsen jurisprudence and Intuitionistic logic are used to avoid the well-known contrary-to-duty (CTD) paradoxes, such as Chisholm paradoxes and its variants. This article uses an intuitionistic version of the ALC description logic, named iALC, to show how an ontology based on individually valid legal statements is able to avoid CTDs by providing models to them.

Contrary-to-Duty Obligations

We investigate under what conditions contrary-to-duty (CTD) structures lacking temporal and action elements can be given a coherent reading. We argue, contrary to some recent proposals, that CTD is not an instance of defeasible reasoning, and that methods of nonmonotonic logics are inadequate since they are unable to distinguish between defeasibility and violation of primary obligations. We pro...

A Paraconsistent Logic for Contrary-to-Duty Imperatives

Contrart-to-duty imperatives are those which tell us what we ought to do if we violate some of our obligations. In this work, we give an inconsistencyfriendly framework for contrary-to-duty imperatives and introduce three semantics for it: static, dynamic and topological. The static semantics uses the standard modal paraconsistent approach whereas the dynamic semantics views violations as dynam...

Normative Requirements and Contrary-to-Duty Obligations