Timeline for What is the most useful non-existing object of your field?
Current License: CC BY-SA 3.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Oct 1, 2014 at 13:01 | comment | added | shuhalo | It is not even an object in your area, because it can't even be defined. | |
| Sep 30, 2014 at 19:47 | comment | added | goblin GONE | This is sometimes called the Russell set, or Russell class. Its so dangerous, even NFU blocks it. | |
| Sep 30, 2014 at 17:35 | comment | added | djechlin | @PeterLeFanuLumsdaine yes, but it's worth pointing out that relative to 19th century set theory, classes are part of hierarchical set theory, which I believe is what Frege tried to rigorize. (Or was it Russell. I'm rusty.) | |
| Sep 29, 2014 at 20:12 | comment | added | Peter LeFanu Lumsdaine | One can also argue that this one does exist, perfectly happily: it’s just a class that isn’t a set. | |
| Sep 29, 2014 at 12:56 | comment | added | Warbo | This is interesting, since it puts the cart before the horse: this set does exist in Frege's set-theory, which Russell used to prove it inconsistent. Russell's set-theory was specifically defined to exclude such objects. Hence the theory is derived from the object's existence, rather than vice versa :) | |
| S Sep 29, 2014 at 10:09 | history | answered | Basil | CC BY-SA 3.0 | |
| S Sep 29, 2014 at 10:09 | history | made wiki | Post Made Community Wiki by Basil |