What would be the most fundamental equations in physics? For example, I know that all of electrodynamics can be obtained from Maxwell's Equations; therefore, Maxwell's Equations would be a complete set of the most fundamental equations of EM. However, something like PV=nRT can be derived from other equations of motion so it is not a fundamental equation. In other words, what is the smallest set of equations from which all of physics could be recovered? Kind of like the equivalent of the ZFC Set Theory axioms (from which, in theory, all of math can be derived) but for physics. I would guess that it would be the Einstein Equation and some equations of the Standard Model.