Dostoevsky 's notebooks show that he had the idea of The Grand Inquisitor after he saw it in a play by Friedrich Schiller , Don Carlos ( 1785-1787 ) . Dostoevsky 's notebooks show that he was inspired to use the figure of the Grand Inquisitor after he encountered it in a play by Friedrich Schiller , Don Carlos ( 1785 â `` 1787 ) .