13 ideas
| 14249 | Boolos reinterprets second-order logic as plural logic [Boolos, by Oliver/Smiley] |
| 10830 | Second-order logic metatheory is set-theoretic, and second-order validity has set-theoretic problems [Boolos] |
| 10829 | A sentence can't be a truth of logic if it asserts the existence of certain sets [Boolos] |
| 10832 | '∀x x=x' only means 'everything is identical to itself' if the range of 'everything' is fixed [Boolos] |
| 10834 | Weak completeness: if it is valid, it is provable. Strong: it is provable from a set of sentences [Boolos] |
| 13841 | Why should compactness be definitive of logic? [Boolos, by Hacking] |
| 10833 | Many concepts can only be expressed by second-order logic [Boolos] |
| 12270 | Being is one [Melissus, by Aristotle] |
| 8978 | Events are made of other things, and are not fundamental to ontology [Bennett] |
| 10364 | Facts are about the world, not in it, so they can't cause anything [Bennett] |
| 3059 | There is no real motion, only the appearance of it [Melissus, by Diog. Laertius] |
| 5100 | The void is not required for change, because a plenum can alter in quality [Aristotle on Melissus] |
| 456 | Nothing could come out of nothing [Melissus] |