  We first write down a very general description of nonlinear classical
electrodynamics, making use of generalized constitutive equations and
constitutive tensors. Our approach includes non-Lagrangian as well as
Lagrangian theories, allows for electromagnetic fields in the widest possible
variety of media (anisotropic, piroelectric, chiral and ferromagnetic), and
accommodates the incorporation of nonlocal effects. We formulate
electric-magnetic duality in terms of the constitutive tensors. We then propose
a supersymmetric version of the general constitutive equations, in a superfield
approach.
