Well... explained rather than resolved.
It has been known for over a hundred years that there is no foundation to mathematics (in particular axiomatic mathematics). While only a handful of axioms are required to define a given axiomatic system - it is impossible to define that handful of axioms in the first place.
This is a pretty large problem. It has generally been ignored because:
1. There didn't seem to be an alternative.
2. "The Empty Set" is pretty obvious even if we can't define it in a non-tautological way.
2. Yeah - a tautology isn't a good starting point.
1. We can directly measure relationships.