Question of axioms

Why do we call quantum physics an ab initio model?

Why do we call classical mechanics an ab initio model?

Is classical electromagnetism an an ab initio model (and if it is one, what are its first principles)?

– Quantum physics : because it is the theory that describes the world at its smallest size with the fewest axioms

– Classical mechanics : because we do not have a “Theory of everything” its the theory we use to describe the world at a macroscopic scale. Also with the fewest axioms

– If we start from Maxwell’s equations we can describe the “whole world” of electromagnetism so we can say that electromagnetism is an ab initio model.

But if we think of Maxwell’s equations as a consequence of another model (like Quantum electrodynamics) we can’t say that electromagnetism is an ab initio model.