Roy, Well, you are correct that the use of axioms in 20th century math and physics involved matters far from obvious, but from a history of thought perspective the concept of an axiom does date back (at least?) to Euclid, for whom they were assumptions thought to be obvious from internal analysis, even if later his axioms (or at least some of them) came to be viewed as synthetic propositions capable of empirical testing. Barkley Rosser