We introduce a natural sequent calculus for preferential conditional logic PCL via embeddings into provability logic GL, achieving optimal complexity and enabling countermodel extraction. Extending the method to PCL with reflexivity and absoluteness – corresponding to Åqvist’s deontic system F with cautious monotony – we employ hypersequents to capture the S5 modality; the resulting calculus subsumes the known calculi for the weaker systems \(\textbf{E} \) and \(\textbf{F} \) within Åqvist family.

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GL-Based Calculi for PCL and Its Deontic Cousin

  • Agata Ciabattoni,
  • Dmitry Rozplokhas,
  • Matteo Tesi

摘要

We introduce a natural sequent calculus for preferential conditional logic PCL via embeddings into provability logic GL, achieving optimal complexity and enabling countermodel extraction. Extending the method to PCL with reflexivity and absoluteness – corresponding to Åqvist’s deontic system F with cautious monotony – we employ hypersequents to capture the S5 modality; the resulting calculus subsumes the known calculi for the weaker systems \(\textbf{E} \) and \(\textbf{F} \) within Åqvist family.