3 ms·

Well, it's not that difficult to fix it in ZF. If you define S to be S = {x in U: x not in x}, then it simply means S is not in U.

• defen 11y ago
  There is no U in ZF so I really don't understand what you are saying.
  • Shaniqua 11y ago
    You can call U anything you want. It's by axiom schema of specification: for any set A, there some set B with a set C in B iff C in A.