Cant you have one system of axioms, and then another, where the corollaries of system A are axioms of system B. Like we derive B's Axioms form A's corollaries (i.e. the axioms of B actually are not axioms in system A, but are derived from system A to form the principles of B).
In that case axioms would be both derived and underived, depending on context. This is a genuine question, I am not that skilled in maths and logics.
For instance (I am guessing out of my depth here) a
Godel sentence may be treated as
an axiom in a system of alternative logic...
e.g. "
this sentence is not provable" is an axiom of a formal system with no further proofs, or
an axiom of a dialtheic logic (i.e. a logic where there can be true contradictions).
So you may (possiblly, if you dont use a paraconsistent logic (ie one which does not allow for ther principle of "explosion")
actually derive the axioms of the first system from a dialtheic logic, because anything follows from a contradiction (according to Bertrand Russls "principle of explosion").
And all formal systems (Godel says?) contain contradictions. So if anything follows from a contradiction,
then the axioms of A follow from the axioms of A, indirectly. Via Godel sentence B.
So axioms can be proven in a roundabout way?
(And they cant, depending on your use of the
Godel sentence.... )
So if we can prove "anything" (ie something like 1+1=2)
then we can prove literally anything (ie any statement, form the consequences of incompleteness and explosion, like 1+1=3, and 1+1=2 , and "the moon ismade from green cheese" etc etc etc ad infinitum)....
so - another educated guess - eventually if we treat the axioms of A as the "set of all sets" (is that even possible... google indicates maybe the thought has been thought before, at leats) it ie the set both contains itself (via deduction of godel sentence B) and it doesnt (via an alternative interpretation of B, where the logic halts)? So we would have a restatement of Russels paradox in terms axioms and proofs? Making it a FRACTAL!!!! So in fact axioms both are (and are not....) axioms, in that they can be proven and cannot. Yet if we prove them, we prove "anything..."
So also we have the
halting problem. In trying to prove the axioms you either halt t "this sentence is unprovable" (1st uinterpretation f Godel sentence)) or you treat it as the starting point for an alternative system in which anything can be derived (according to the contradiction interpretation of Godel sentence), including the "proof" of the first axioms A....maybe, but also an arbitrarily large system of alternatives from which there is no escape?
If you have deductive closure (ie a logical concept meaning you are commited to what can be deduced from your beliefs) then it is true that axioms (and all else in the system, maybbe) cannot be proven...
the
search for proof halts as a Godel sentence; OR: or it continues in another logical guise where infinity rules and the program runs for ever inder a different interpretation of that self same sentence...
Wittgenstein mantioned that
logical grammar is (or at least could be) arbitrary:
How many ways to play "rock paper scissors" folks?