18 ideas
| 7548 | Classes, grouped by a convenient property, are logical constructions [Russell] |
| 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] |
| 7545 | Visible things are physical and external, but only exist when viewed [Russell] |
| 7553 | Sense-data are purely physical [Russell] |
| 7549 | If my body literally lost its mind, the object seen when I see a flash would still exist [Russell] |
| 7546 | A man is a succession of momentary men, bound by continuity and causation [Russell] |
| 7550 | We could probably, in principle, infer minds from brains, and brains from minds [Russell] |
| 20721 | Punctuality and justice in dealings are excellent for raising a man in the world [Franklin] |
| 20720 | Time is money, ..credit is money, ..and money breeds more money [Franklin] |
| 7551 | Matter is a logical construction [Russell] |
| 7547 | Matter requires a division into time-corpuscles as well as space-corpuscles [Russell] |
| 7552 | Six dimensions are needed for a particular, three within its own space, and three to locate that space [Russell] |