more from Theodore Sider

Single Idea 13712

[catalogued under 4. Formal Logic / D. Modal Logic ML / 5. Epistemic Logic]

Full Idea

Epistemic accessibility should be required to be reflexive (allowing Kφ→φ). S4 allows the 'KK principle', or 'positive introspection' (Kφ→KKφ), and S5 allows 'negative introspection' (ČKφ→KČKφ).

Clarification

KK is knowing that you know (or that you don't know)

Gist of Idea

Epistemic accessibility is reflexive, and allows positive and negative introspection (KK and KČK)

Source

Theodore Sider (Logic for Philosophy [2010], 7.2)

Book Reference

Sider,Theodore: 'Logic for Philosophy' [OUP 2010], p.185