Quantum physics is called an ab initio model because it is derived directly from fundamental principles, specifically from the Schrödinger equation, Heisenberg’s uncertainty principle, and the quantization of physical properties (such as energy levels). Classical mechanics is also considered an ab initio model. It is based on Newton’s laws of motion (or more generally on the Lagrangian or Hamiltonian formulations). classical electromagnetism is also considered an ab initio model. It is based on Maxwell’s equations, which are derived from basic principles about the behavior of electric and magnetic fields.