2001 | Modal Logic |
7.1 | p.137 | 14970 | Normal system K has five axioms and rules |
7.1.1 | p.140 | 14971 | D is valid on every serial frame, but not where there are dead ends |
7.1.2 | p.141 | 14974 | A relation is 'Euclidean' if aRb and aRc imply bRc |
7.1.2 | p.141 | 14972 | S4 has 14 modalities, and always reduces to a maximum of three modal operators |
7.1.2 | p.141 | 14973 | In S5 all the long complex modalities reduce to just three, and their negations |
7.2.1 | p.149 | 14975 | A de dicto necessity is true in all worlds, but not necessarily of the same thing in each world |
7.2.2 | p.151 | 14976 | Reject the Barcan if quantifiers are confined to worlds, and different things exist in other worlds |