"Shmuel (Seymour J.) Metz" wrote: > > In <firstname.lastname@example.org>, on 03/30/2013 > at 08:35 AM, David C. Ullrich <email@example.com> said: > > >Oh? For example? > > <http://en.wikipedia.org/wiki/New_Foundations> > > Note that it has only a restricted axiom of comprehension.
David Ullrich might be interested to know that NF proves infinity and disproves choice! NF with Urelemente (and thus with Extensionality relaxed) does neither. (Assuming NF/NFU to be consistent, natr\"ulich. I think NFU is consistent iff PA is, and the consistency of NF is open.)
-- When a true genius appears in the world, you may know him by this sign, that the dunces are all in confederacy against him. Jonathan Swift: Thoughts on Various Subjects, Moral and Diverting