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Four kinds of modality for possible-world semantics

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Modal logic is primarily defined in terms of its contribution of notation for the modal categores of possibility and necessity. Yet there are two heads under which this distinction can be analyzed: "De dicto" possibility/necessity and "de re" possibility/necessity. "De dicto" has reference to the modality of a sentence whereas "de re" has reference to the modality of a thing (Steinhart, p. 98-99). A de dicto necessity, for example, says that the sentence "Felipe is from panama" is true in all possible worlds. A de dicto possibility says that the sentence "Felipe is from Panama" is possibly. true. But what does it mean to be possibly true? "A sentence is possibly true if, and only if, it is true at some world"(Steinhart, p. 99). The sentence "Felipe is from Panama" might be true in world 1, but he might not be from panama in world 2, whereas a de dicto necessity insists that Felipe is from Panama in all possible worlds.

De re concerns properties of objects rather than truth-values of sentences(Steinhart, p. 99). So for example, in a de re necessity, the object "Felipe" might possess the property of being Panamanian in all possible worlds. A de re possibility, however, might entail that Felipe possesses a property other than being from Panama in another possible world. He might, in another world, possess the property of being from America. A de re possibility affirms that Felipe has the property of being from Panama in at least one world, but there may be other worlds in which Felipe does not possess the property of being from Panama.

Steinhart, Eric. "More Precisely: The Mathematics You Need To Do Philosophy." Broadview Press, 2009

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