The current book of Isaiah (Hebrew: ישעיהו / Y’shuay’hu “YHWH saves”, Greek: ισαιας / isaias) has at least two different authors. The original Isaiah constitutes chapters 1 – 39. What is called “Deutero-Isaiah” (second Isaiah) makes up chapters 40 – 66. The themes of destruction, exile and suffering are presumed in Deutero-Isaiah; there is familiarity with the history of the 6th century, above all with Cyrus as the anointed one/christ/messiah, and firsthand experience of Babylonian religion; and a prophet speaks both out of and into the situation of his contemporaries. There are the themes of comfort and salvation, a new salvation under a new covenant; God is presented as creator and maker, and his action in history as redeemer and savior is rooted in his action as creator. Chaps. 40-66 there is constant repetition and doubling of words; there is familiarity with the style of the psalms of descriptive praise with their heaping up of present participles; Jerusalem, Israel (the suffering servant of Isa. 52-53), and objects are personified. Deutero-Isaiah might have been written by a student of the original pre-exile Isaiah. In the time of Isaiah, Babylon was seen as a friendly nation; it was Assyria that was the threat (chapter 39).
There are arguments for a Trito-Isaiah (third Isaiah) which comprises chapters 55 – 66. Throughout the greater part of Trito-Isaiah we continually find ourselves in the community of the restoration: there is mention of the temple and of rebuilding it, of sacrifices, of the observance of the sabbath and the regulations of the Torah, and this observance is considered to be an essential qualification for membership of the community. None of these arguments appears even once in Deutero-Isaiah, and since the setting of Deutero-Isaiah is Babylon, it is difficult to see how that would be possible. Trito-Isaiah was written probably 20 years after Deutero-Isaiah. In 60:13 the temple has been built and it is only necessary to adorn it, implying a post-exile Persian era setting.