Contrary-to-duty reasoning with preference-based dyadic obligations

Abstract

In this paper we introduce Prohairetic Deontic Logic (PDL), a preferencedbased dyadic deontic logic. In our preferencedbased interpretation of obligations “a should be (done) if b is (done)” is true if (1) no ¬a ∧ b state is as preferable as an a ∧ b state and (2) the preferred b states are a states. We show that this representation solves different problems of deontic logic. The first part of the definition is used to formalize contrarydtodduty reasoning, which, for example, occurs in Chisholm’s and Forrester’s notorious deontic paradoxes. The second part is used to make deontic dilemmas inconsistent.