3 May
2006
3 May
'06
6:30 p.m.
Franklin wrote: << The normal axioms of set theory don't require [that a set cannot be a member of itself]. I'm not sure which axioms you're thinking of, but the Axiom of Regularity of Zermelo-Frankel set theory (cf. http://en.wikipedia.org/wiki/Axiom_of_regularity) does indeed imply that no set can be a member of itself. --Dan