  Duhem proceeds to detail two complete theories that can recover Maxwell’s equations within a logical and coherent structure, the theories of Boltzmann and Helmholtz. The only criterion he gives for choosing between these two theories, though without elaborating upon it or justifying it, is that Helmholtz’s theory is to be preferred over Boltzmann’s theory because it is a natural “extension of the doctrines of Poisson, Ampere, Weber, and Newmann; it leads logically from the principles posited at the start of the nineteenth century to the most seductive consequences of Maxwell’s theories, from the laws of Coulomb to the electromagnetic theory of light; [it does so] without losing any of the recent victories of electrical science; it reestablishes the continuity of tradition” (1902, 225).