the task of identifying the basic postulates of these equations *loses* its meaning. On the contrary, the reversed procedure starting with retarded potentials can help to elucidate the nature of these postulates. In the task of finding these potentials, we have argued that charge conservation should be considered the fundamental axiom underlying Maxwell’s equations.

Clearly, the interest sketched by Feynman in his handwritten notes was how to obtain Maxwell’s equations by starting with potentials and using physical principles like relativity and charge conservation. In this aim we think the recourse of heuristic arguments is unavoidable. Put differently, the procedure followed by De Luca et al. [@3] to arrive at the Lorenz force and the homogeneous Maxwell’s equation as well as our procedure to arrive at the inhomogeneous and homogeneous Maxwell’s equations could be interpreted as *constructive* procedures. *In this kind of procedures one makes use of heuristic arguments to show the *existence* of a mathematical object by providing a method for creating the object.* Of course, one generally has knowledge of this object by other means. In this perspective, our procedure to obtain Maxwell’s equations could be considered as a constructive method to demonstrate the existence of retarded potentials which 