"By definition" is the only possible justification, as for any other axiom in mathematics. Your intuition that such a thing is 'poor' and that there is a 'bette

"By definition" is the only possible justification, as for any other axiom in mathematics. Your intuition that such a thing is 'poor' and that there is a 'better' (why, more natural?, ordained by a divine source?) way to do it, is wrong.