It asserts about sets that are not its members.
No. It does not say anything about any other set but the empty set. The assertion that the empty set has no elements is a property of the empty set alone.
Definition: The
empty set is the set that has no elements.
You're not understanding the meaning of the implied universal quantifier here. This definition is really saying: "for all sets X, X is not an element of the empty set". Using the universal quantifier to say "for all sets X" is equivalent to saying "if a set X exists". Worded differently:
Definition: The
empty set is the set such that if a set X exists then X is not an element of the empty set.
This is just a definition. There's nothing circular about it. Now for the axiom:
Axiom: The
empty set exists.
Worded differently, with the definition of
empty set substituted, and letting {} denote the
empty set:
Axiom: The set {}, such that if a set X exists then X is not an element of {}, exists.
Now, the axiom tells us that {} exists: the set that does not contain a set X if X exists.
At this point, we only know that one set, {}, exists. And by definition of {}, {} is not an element of {} (let X = {} to obtain this statement).
Because we only know the existence of one set ({}) at this point, it is invalid logic to deduce a proposition involving any other set like you keep doing. The only useful proposition you can possibly deduce at this point is the one I just did about {} not being an element of itself.
There is no contradiction here for the reason that the definition of the empty set
only asserts something about sets that are already known to exist.
It does not say anything about sets that are not known to exist in the axiomatic system at this point, including the set {{}}.
I cannot put it more plainly Doron. Either you get it, or you don't. I'm not the one who came up with this stuff, centuries of ingenious mathematicians did. Either every mathematician in the world is wrong, or you simply can't understand something as basic as the Axiom of the Empty Set.