15 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] |
| 23651 | Universals are not objects of sense and cannot be imagined - but can be conceived [Reid] |
| 23650 | Only individuals exist [Reid] |
| 23649 | No one thinks two sheets possess a single whiteness, but all agree they are both white [Reid] |
| 11874 | Real identity admits of no degrees [Reid] |
| 23652 | We must first conceive things before we can consider them [Reid] |
| 23648 | First we notice and name attributes ('abstracting'); then we notice that subjects share them ('generalising') [Reid] |
| 1748 | Archelaus was the first person to say that the universe is boundless [Archelaus, by Diog. Laertius] |
| 5989 | Archelaus said life began in a primeval slime [Archelaus, by Schofield] |