12 ideas
| 14970 | Normal system K has five axioms and rules [Cresswell] |
| 14971 | D is valid on every serial frame, but not where there are dead ends [Cresswell] |
| 14972 | S4 has 14 modalities, and always reduces to a maximum of three modal operators [Cresswell] |
| 14973 | In S5 all the long complex modalities reduce to just three, and their negations [Cresswell] |
| 14976 | Reject the Barcan if quantifiers are confined to worlds, and different things exist in other worlds [Cresswell] |
| 8978 | Events are made of other things, and are not fundamental to ontology [Bennett] |
| 12741 | If experience is just a dream, it is still real enough if critical reason is never deceived [Leibniz] |
| 12740 | The strongest criterion that phenomena show reality is success in prediction [Leibniz] |
| 14974 | A relation is 'Euclidean' if aRb and aRc imply bRc [Cresswell] |
| 14975 | A de dicto necessity is true in all worlds, but not necessarily of the same thing in each world [Cresswell] |
| 12721 | Light, heat and colour are apparent qualities, and so are motion, figure and extension [Leibniz] |
| 10364 | Facts are about the world, not in it, so they can't cause anything [Bennett] |