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Ideas of Max J. Cresswell, by Text

[New Zealand, fl. 1968, At Victoria Univesity, Wellington, NZ.]

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