Timeline for Logical problems in category theory
Current License: CC BY-SA 2.5
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 4, 2010 at 5:19 | comment | added | Reid Barton | We must be having some terminological misunderstanding, because that article implies that the collection of all semigroupoids doesn't form a semigroupoids, because a semigroupoid has a set of objects. | |
| Jan 3, 2010 at 20:31 | comment | added | Adam | en.wikipedia.org/wiki/Semigroupoid Sets have vastly more structure than semigroupoids. For example, the category of sets is cartesian closed (a fact which is used in the proof of Russell's paradox) while the category of semigroupoids is not. | |
| Jan 3, 2010 at 16:20 | comment | added | Reid Barton | I don't know what a semigroupiod is, but why should one be any more able to state that fact than "the collection of all sets is a set", and what's wrong with instead stating the equivalent of "the collection of all U-sets is a V-set, where U and V are Grothendieck universes with U in V"? | |
| Jan 3, 2010 at 7:40 | comment | added | Adam | I don't know if they're always effective. The collection of all semigroupoid homomorphisms themselves form a semigroupoid (under composition), and one cannot state this fact -- even using universes. It is disturbing to have a proposition be neither true nor false but simply arbitrarily excluded from consideration like that. | |
| Jan 3, 2010 at 2:50 | vote | accept | Anweshi | ||
| Jan 4, 2010 at 23:02 | |||||
| Jan 2, 2010 at 22:53 | history | answered | Reid Barton | CC BY-SA 2.5 |