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Full Idea
We can say of a wooden table that it would have been possible for it to have originated from some different matter, even though it is not actually possible. So what is necessary fails to be necessarily necessary, and S4 modal logic is fallacious.
Gist of Idea
What is necessary is not always necessarily necessary, so S4 is fallacious
Source
Nathan Salmon (The Logic of What Might Have Been [1989], I)
Book Ref
Salmon,Nathan: 'Metaphysics, Mathematics and Meaning' [OUP 2005], p.131
A Reaction
[compressed]
| 15544 | If what is actual might have been impossible, we need S4 modal logic [Armstrong, by Lewis] |
| 14972 | S4 has 14 modalities, and always reduces to a maximum of three modal operators [Cresswell] |
| 16958 | In S4 the actual world has a special place [Dummett] |
| 14671 | What is necessary is not always necessarily necessary, so S4 is fallacious [Salmon,N] |
| 9747 | The system S4 has the 'reflexive' and 'transitive' conditions on its accessibility relation [Fitting/Mendelsohn] |
| 7794 | There are seven modalities in S4, each with its negation [Girle] |
| 15102 | S4 says there must be some necessary truths (the actual ones, of which there is at least one) [Cameron] |