Concept tag
#s5
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S5 is the right logic for metaphysical necessity
Here is a view I hold about modal logic and want tested. S5 says: whatever is possible is necessarily possible, and whatever is necessary is necessarily necessary. In Kripke's terms, every world is accessible from every other. For metaphysical necessity (what could…
Started by Tomasz Szewczak6 replies -
How did Kripke’s possible worlds turn S4 and S5 from arbitrary axioms into something meaningful?
I've been reading about modal logic for fun. I understand the operators. What I don't understand is the history I keep seeing summarised: C. I. Lewis invented several systems, S1 to S5, with different axioms; nobody could say which was "correct" or…
Started by Pieter van Dijkhuizen4 replies