Want to take part in these discussions? Sign in if you have an account, or apply for one below
Vanilla 1.1.10 is a product of Lussumo. More Information: Documentation, Community Support.
Added description about the two possible types of atoms. The section on the category-theoretic approach should probably be moved to a separate page, since it is about Fraenkel-Mostowski models in particular, and not so much about ZFA itself.
Calling reflexive sets “atoms” seems to me to be a contradiction in terms; aren’t atoms supposed to be things that aren’t sets?
It would be good to have a separate, more detailed page on FM models, but an outline at ZFA is not out of place, to my mind, at least at present.
Calling reflexive sets “atoms” seems to me to be a contradiction in terms; aren’t atoms supposed to be things that aren’t sets?
I agree that the first thing that comes to mind when someone mentions “atoms” would be “empty” atoms, but I guess reflexive/Quine atoms do play the role of atoms in ZFA, and it appears to be standard to call them Quine atoms. I have carefully worded the idea sections to say atoms are not made up of other sets, rather than having no elements.
It would be good to have a separate, more detailed page on FM models, but an outline at ZFA is not out of place, to my mind, at least at present.
Yes I agree. My main objection was that it appeared to claim it is a category-theoretic approach to ZFA, while it is actually a category-theoretic approach to FM models, and this distinction was not made clear in the paragraph as well.
I’ve created a new page for FM models, and moved the relevant content there. A small paragraph was added to the ZFA page to mention FM models.
Expanded a bit on empty atoms.
Wikipedia says ZFA, and I’ve seen similar before. That seems to be what is accepted in English.
Or course ur-elements or urelemente should be mentioned in the article. (Edit: And, they are.)
ZFU is how I know this theory. I’ve added in parentheses:
…called atoms or urelements (hence the alternative name ZFU)…
Jech’s Set Theory (and the Springer LNM precursor) uses ’ZFA’, and that’s a pretty standard reference.
[Administrative note: merged two threads so that the discussion page has the historical discussion.]
1 to 12 of 12