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

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

This revised version was published online in June 2006 with corrections to the Cover Date.