A note on de re modalities (Q2735834)

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scientific article; zbMATH DE number 1641320
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A note on de re modalities
scientific article; zbMATH DE number 1641320

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    4 September 2001
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    de re modality
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    de dicto modality
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    normal system
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    A note on de re modalities (English)
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    An extension of a result by \textit{G. E. Hughes} and \textit{M. J. Cresswell} [A new introduction to modal logic. Routledge, London (1996; Zbl 0855.03002)] is proved. Hughes and Cresswell showed that de re modalities are not eliminable in any system contained in S5. It is shown here that for every normal system S, except Triv, Ver and their intersection, de are modalities are not eliminable in \(\text{S}+ \text{BF}\).
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