Single Idea 18825

[catalogued under 10. Modality / A. Necessity / 6. Logical Necessity]

Full Idea

I accept the widely held thesis that S5 is the logic of logical necessity.

Clarification

S5 is the most universal of the modal logics

Gist of Idea

S5 is the logic of logical necessity

Source

Ian Rumfitt (The Boundary Stones of Thought [2015], 6.4 n16)

Book Reference

Rumfitt,Ian: 'The Boundary Stones of Thought' [OUP 2015], p.166


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.