23 ideas
10482 | The logic of ZF is classical first-order predicate logic with identity [Boolos] |
10492 | A few axioms of set theory 'force themselves on us', but most of them don't [Boolos] |
9193 | ZF set theory has variables which range over sets, 'equals' and 'member', and extensionality [Dummett] |
9194 | The main alternative to ZF is one which includes looser classes as well as sets [Dummett] |
15510 | Classes are a host of ethereal, platonic, pseudo entities [Goodman] |
10485 | Naïve sets are inconsistent: there is no set for things that do not belong to themselves [Boolos] |
10484 | The iterative conception says sets are formed at stages; some are 'earlier', and must be formed first [Boolos] |
9920 | Two objects can apparently make up quite distinct arrangements in sets [Goodman, by Burgess/Rosen] |
10657 | The counties of Utah, and the state, and its acres, are in no way different [Goodman] |
9195 | Intuitionists reject excluded middle, not for a third value, but for possibility of proof [Dummett] |
9186 | First-order logic concerns objects; second-order adds properties, kinds, relations and functions [Dummett] |
9187 | Logical truths and inference are characterized either syntactically or semantically [Dummett] |
9191 | Ordinals seem more basic than cardinals, since we count objects in sequence [Dummett] |
10491 | Infinite natural numbers is as obvious as infinite sentences in English [Boolos] |
10483 | Mathematics and science do not require very high orders of infinity [Boolos] |
9192 | The number 4 has different positions in the naturals and the wholes, with the same structure [Dummett] |
10490 | Mathematics isn't surprising, given that we experience many objects as abstract [Boolos] |
10488 | It is lunacy to think we only see ink-marks, and not word-types [Boolos] |
7956 | If all and only red things were round things, we would need to specify the 'respect' of the resemblance [Goodman, by Macdonald,C] |
7957 | Without respects of resemblance, we would collect blue book, blue pen, red pen, red clock together [Goodman, by Macdonald,C] |
7952 | If we apply the same word to different things, it is only because we are willing to do so [Goodman, by Macdonald,C] |
10487 | I am a fan of abstract objects, and confident of their existence [Boolos] |
10489 | We deal with abstract objects all the time: software, poems, mistakes, triangles.. [Boolos] |