Ab initio way

“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 and classical mechanics are ab initio models because we already have complete mathematical descriptors of natures behaviors. Classical electromagnetism is an ab initio model that comes from classical magnetics and the wave-particle duality of light.