Ab initio way

In science, a model is ab initio if it only relies on the fundamental laws of nature. For example, quantum physics is an ab initio model because you start with the Schrodinger equation, and the only input you need in this equation are the fundamental constants of nature and the mass of the atoms involved. Classical mechanics can be considered an ab initio method, in fact it relies on the Newton equations, but you often need empirical data in order to solve it. Classical electromagnetism is an ab initio model, in fact it only relies on Maxwell’s equations and it can’t be reduced to more fundamental concepts.