If we know that the Polarization P in LIH dielectrics is proportional to the net field inside the dielectric according to: P = ε0χeE.....(1) And we know that D = εE........(2) Does it not follow that we can ascertain the polarization directly from the applied (free charge) field, since we can relate D to E, and then E to P? The author of my electrodynamics text (Griffiths), says that we cannot. His explanation being that once we place dielectric in an external field E0, the material will polarize and create an opposing field to the applied field, which in turn modifies the polarization again because it changes the total field that the atoms/molecules in the material are being subject to, and this process repeats over and over. In actuality, are these two quantities (E and P) in some sort of dynamic equilibrium within the material? If so, how come (1) and (2) are valid?