Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Defeasible Modalities   Nonmonotonic logics are usually characterized by the presence of some notion
of 'conditional' that fails monotonicity. Research on nonmonotonic logics is
therefore largely concerned with the defeasibility of argument forms and the
associated normality (or abnormality) of its constituents. In contrast,
defeasible modes of inference aim to formalize the defeasible aspects of modal
notions such as actions, obligations and knowledge. In this work we enrich the
standard possible worlds semantics with a preference ordering on worlds in
Kripke models. The resulting family of modal logics allow for the elegant
expression of defeasible modalities. We also propose a tableau calculus which
is sound and complete with respect to our preferential semantics.

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The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: astro-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: stat
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin