Superposition of displacement fields?

[Wheelwalker]

This isn't a homework question, however I'm curious if displacement fields can simply be added to find the total displacement field at some point. My instinct tells me this should be true. For linear media, D=εE. Since electric fields can be superimposed upon each other, shouldn't the same be true for displacement fields?

 

[Goddar]

Certainly true for linear media. For the non-linear case, i would say it's still true since:
D = E + 4πP (Gaussian units), P = <d>/V (average dipole moment per unit volume) and since d is a sum over point-charges...