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2 ideas
18816 | Metaphysical modalities respect the actual identities of things [Rumfitt] |
Full Idea: The central characteristic mark of metaphysical necessity is that a metaphysical possibility respects the actual identities of things - in a capacious sense of 'thing'. | |
From: Ian Rumfitt (The Boundary Stones of Thought [2015], 3.4) | |
A reaction: He contrast this with logical necessity, and concludes that some truths are metaphysically but not logically necessary, such as 'Hesperus is identical with Phosphorus'. Personally I like the idea of a 'necessity-maker', so that fits. |
18825 | S5 is the logic of logical necessity [Rumfitt] |
Full Idea: I accept the widely held thesis that S5 is the logic of logical necessity. | |
From: Ian Rumfitt (The Boundary Stones of Thought [2015], 6.4 n16) | |
A reaction: It seems plausible that S5 is also the logic of metaphysical necessity, but that does not make them the same thing. The two types of necessity have two different grounds. |