We know that $D=\epsilon_0 E+P$ where'D' is the electric displacement field and takes into account the field due to free carriers.'P' is the polarization and takes into account the field due to bounded charges and 'E' is the fundamental electric field and accounts for both effects of free carriers and bounded charges.
So, shouldn't the 'P' be subtracted from 'E' rather than adding ? Also what is the value of 'D' in vacuum and in a conductor and why ?
Also is displacement current the time rate of change of electric field(E) or electric displacement field(D) ?