> I am yet to find a lucid and intuitive explanation of why we need both E and D for the electric field and B and H for the magnetic field. E alone cannot desc

> I am yet to find a lucid and intuitive explanation of why we need both E and D for the electric field and B and H for the magnetic field. E alone cannot describe fully state of dielectric, and B alone cannot fully describe state of magnetic medium. We need additional concepts, either charge/current densities, or polarization/magnetization, or D/H, in that order of importance. In modern understanding, D and H are auxiliary concepts that are useful mainly in special but important cases they were historically devised for. Let's take D for example. If free charge is absent, Maxwell's equations imply very nice equation div D = 0. The equation for E is more complicated (includes bound charge density that is hard to measure, hard to relate to other things in the model and so is usually preferred to be ignored). If in addition the medium is linear (a special but important case), D is a simple linear function of E ( there is no such simple relation to charge density or current density) so things such as the concept of EM energy in medium is possible, and wave propagation in crystals can be analyzed most elegantly. Sure, all could be analyzed in terms of E and rho and j which would be more "physical" but it is not the most elegant way to do it. It is like in mechanics: we can analyze complicated systems with constraints by writing down many equations involving constraint forces, but there are easier methods such as the Lagrangian.