18 ideas
| 19115 | You can 'rebut' an argument's conclusion, or 'undercut' its premises [Antonelli] |
| 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] |
| 19119 | We infer that other objects are like some exceptional object, if they share some of its properties [Antonelli] |
| 19111 | Reasoning may be defeated by new premises, or by finding out more about the given ones [Antonelli] |
| 19114 | Should we accept Floating Conclusions, derived from two arguments in conflict? [Antonelli] |
| 19113 | Weakest Link Principle: prefer the argument whose weakest link is the stronger [Antonelli] |
| 19116 | Non-monotonic core: Reflexivity, Cut, Cautious Monotonicity, Left Logical Equivalence, Right Weakening [Antonelli] |
| 19117 | We can rank a formula by the level of surprise if it were to hold [Antonelli] |
| 19118 | People don't actually use classical logic, but may actually use non-monotonic logic [Antonelli] |
| 19110 | In classical logic the relation |= has Monotony built into its definition [Antonelli] |
| 19112 | Cautious Monotony ignores proved additions; Rational Monotony fails if the addition's negation is proved [Antonelli] |
| 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] |
| 22489 | 'Good' is an attributive adjective like 'large', not predicative like 'red' [Geach, by Foot] |