|Modalities: modalities are in modal logic possibility, necessity and contingency.|
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Relative modality/Lewis: limited to areas of possible worlds.
Necessity/possibility: are just the dual pair of relative arrangements whose characteristic relation is the two-digit general (universal) relation between worlds.
Die Identität von Körper und Geist Frankfurt 1989
Konventionen Berlin 1975
Philosophical Papers Bd I New York Oxford 1983
Philosophical Papers Bd II New York Oxford 1986
Cl. I. Lewis
Mind and the World Order: Outline of a Theory of Knowledge (Dover Books on Western Philosophy) 1991