more from M Fitting/R Mendelsohn

### Single Idea 9748

#### [catalogued under 4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5]

Full Idea

The system S5 has the 'reflexive', 'symmetric' and 'transitive' conditions imposed on its accessibility relation - that is, every world is self-accessible, and accessibility is mutual, and it carries over a series of worlds.

Gist of Idea

System S5 has the 'reflexive', 'symmetric' and 'transitive' conditions on its accessibility relation

Source

M Fitting/R Mendelsohn (First-Order Modal Logic [1998], 1.8)

Book Reference

Fitting,M/Mendelsohn,R: 'First-Order Modal Logic' [Synthese 1998], p.19

A Reaction

S5 has total accessibility, and hence is the most powerful system (though it might be too powerful).