Single Idea 15027

[catalogued under 10. Modality / C. Sources of Modality / 3. Necessity by Convention]

Full Idea

If □φ says that φ is true by convention, then □φ would apparently turn out to be contingent, since statements about what conventions we adopt are not themselves true by convention. The main axioms of S4 and S5 would be false.

Gist of Idea

If truths are necessary 'by convention', that seems to make them contingent

Source

Theodore Sider (Writing the Book of the World [2011], 12.1)

Book Reference

Sider,Theodore: 'Writing the Book of the World' [OUP 2011], p.268


Related Idea

Idea 15000 'It is raining' and 'it is not raining' can't be legislated, so we can't legislate 'p or ¬p' [Sider]