In 1956 a fundamental paper on the elastic dielectric, authored by RA Toupin appeared in the Archive of Rat. Mech. and Analysis. Toupin's main idea was to substitute the concept of constitutive equation between the polarization P and the electric field E with an equilibrium equation. Formally, the mathematical description of the dielectric behaviour does not change with respct to the classical theory as far as one is concerned with electrostatics, but it does in electrodynamics. Furtherly, RD Mindlin and GA Maugin developed and generalized the method of virtual powers, showing the very important role played by the gradient of polarization. However, Toupin's idea, though ingeniuos and very powerful, is not completely new since Ottaviano Fabrizio Mossoti, in 1836, by proposing the method of the 'cavity', established an electrical equilibrium equation.