Why defeasible deontic logic needs a multi preference semantics

  • Yao-Hua Tan
  • Leendert W. N. der Torre
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 946)


There is a fundamental difference between a conditional obligation being violated by a fact, and a conditional obligation being overridden by another conditional obligation. In this paper we analyze this difference in the multi preference semantics of our defeasible deontic logic DefDiode. The semantics contains one preference relation for ideality, which can be used to formalize deontic paradoxes like the Chisholm and Forrester paradoxes, and another preference relation for normality, which can be used to formalize exceptions. The interference of the two preference orderings generates new questions about preferential semantics.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1995

Authors and Affiliations

  • Yao-Hua Tan
    • 1
  • Leendert W. N. der Torre
    • 1
    • 2
  1. 1.EuridisErasmus University RotterdamDR RotterdamThe Netherlands
  2. 2.Tinbergen Institute and Department of Computer ScienceErasmus University RotterdamDR RotterdamThe Netherlands

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