Necessity and Relative Contingency |
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Authors: | Claudio Pizzi |
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Institution: | (1) Dipartimento di Filosofia e Scienze Sociali, Università di Siena, via Roma 47, 53100 Siena, Italy |
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Abstract: | The paper introduces a contingential language extended with a propositional constant τ axiomatized in a system named KΔτ ,
which receives a semantical analysis via relational models. A definition of the necessity operator in terms of Δ and τ allows
proving (i) that KΔτ is equivalent to a modal system named K□τ (ii) that both KΔτ and K□τ are tableau-decidable and complete with respect to the defined relational semantics (iii) that the modal τ -free fragment of KΔτ is exactly
the deontic system KD. In §4 it is proved that the modal τ -free fragment of a system KΔτw weaker than KΔτ is exactly the
minimal normal system K.
Presented by Daniele Mundici |
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Keywords: | Contingency relative necessity propositional constants semantic tableaux |
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