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Single Idea 15102

[filed under theme 4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / g. System S4 ]

Full Idea

S4 says there must be some necessary truths, because the actual necessary truths must be necessary. (It says if there are some actual necessary truths then that is so - but the S4 axiom is an actual necessary truth, if true).

Gist of Idea

S4 says there must be some necessary truths (the actual ones, of which there is at least one)

Source

Ross P. Cameron (On the Source of Necessity [2010], 2)

Book Ref

'Modality', ed/tr. Hale,B/Hoffman,A [OUP 2010], p.140