This monograph enquires into the unity of the Book of Isaiah. Was the final text of Isaiah intended to give an answer to the prophet Nathan's questioning of YHWH's faithfulness to his promises to David (II Sam 7)? The background to Nathan's prophecy - anchored above all in the union between the Royal House of David and the House of YHWH - forms the thread leading the reader through the 66 chapters of the Book of Isaiah and presenting it as the inheritance of the promise. The added meaning given by the final redaction in its turn poses the question of the role played by redactors in the prophetic literature.