I've been reading through Isaiah, and I've just started the second half of the book (chs.40-66). Contemporary scholarship generally assumes these chapters are not written by the 8th century prophet Isaiah, despite the book's seeming attribution of the book to him. The main reason is that they seem to be about a time much later, the return from exile in the 6th century. Stylistic considerations are also cited, but this turns out to be a bit of ad hoc special pleading, since the same stylistic features are present throughout the first half of the book, and these scholars then pull themselves up on their own bootstraps by insisting that those earlier chapters must also be later additions. At some points this gets even as ridiculous as to minimize the contributions of Isaiah to only a very small component of the overall material even of chapters 1-35. It's taken rather to be the additions of this great school Isaiah must have founded, and thus it gets attached to his book because it's in the Isaianic prophetic school. All this makes me wonder what was so great about Isaiah to have merited this great school attributing all these great prophecies to him if what he actually did was only this tiny amount of material, none of it resembling in content most of the stuff that somehow ended up getting attributed to him.
Suffice it to say that I'm not even close to convinced that Isaiah did not write these chapters. He may not have delivered them as addresses, as he did the earlier chapters in the book, but the argument that he couldn't have written the second half of the book doesn't leave me very convinced, which leaves me taking the text's claim as the most important evidence available, and all the text does is introduce the book as the prophecy of Isaiah, with no new introduction of a new unit with other author information once you hit this second major section.
As I was reading chapter 42 this morning, something occurred to me that I hadn't thought of before.
There's a great deal of attention in this part of the book to the issue of idolatry, in particular to the fruitlessness of worshiping pieces of wood, rock, and metal in the light of the inability of such things to do anything but just sit there. In the mainstream view, this is a sign of the late theology of the post-exilic period that takes the God of Israel to be the only divine being rather than the henotheistic perspective that they take to have been assumed in earlier times, according to which every people-group had a god or gods, and all of them existed, but Israel's god was simply more powerful than the others in his own territory.
According to the mainstream view, the belief in one omnipotent God came in as a result of the clear implication that a henotheistic, local god would be problematic if the people got moved into exile in Babylon. Of course some people clearly were influenced by this mindset in the surrounding nations. See Psalm 137. But that doesn't mean it was the orthodox view in Israel, and it doesn't mean the monotheism portrayed in the Torah and prophets were not there all along.
One piece of evidence against this reconstruction, and particularly against the view that Isaiah 40-66 was composed long after the death of Isaiah by other people over a fairly long time, is the emphasis on idolatry in these chapters. God is held up in contrast to idols, as if idols were a major problem among the community. This would seem to be a little odd if monotheism were simply assumed by all Israel, as is generally taken to be the case by scholars of the post-exilic period.
Look at the indisputably post-exilic prophets Haggai, Zechariah, and Malachi. The problems they point out among the returned exiles seem unrelated to idolatry. The post-exilic Chronicles somewhat deemphasizes the sin of idolatry and emphasizes the continuing promises to Israel, arguing for continuity between the post-exilic community and the monarchic period. It's as if that issue isn't as relevant, and thus the polemic against kings who tolerated or engaged in idolatry is not the focus, even if it's sometimes present. The book of Ezra-Nehemiah makes no mention of idolatry, as far as I remember. The only remotely connected issue is the marrying of foreign wives, leading to the raising of children outside the context of the covenant with Israel.
I'm not assuming that a polemic against idols would have been useless or irrelevant in the post-exilic period. Emphasizing that foreign gods are not real would be of great value to those who needed to be reminded that their God is the only divine being with any power. But the argument against idolatry in these chapters of Isaiah seems to me to be far more important to the author than I would expect of someone who had already gone through the period of exile, return, and restoration that someone in the post-exilic period would have.
A reconstruction that seems more likely to my mind is that the inclusion of arguments against idolatry serves as a way to tie the message of future exile and return back to those who would have these words even before the exile. If Isaiah had been given a vision of these events that would occur well into the future of his time, it would make sense for his oracles to include not just forecasts of the exile (as the end of ch.42 has, for example) and return (as much of the material in chs.40-48 had) but also material about some of the direct relevance of all of this for those in the community that still has yet to be judge via the exile, and one of those applications in Isaiah's mind is that if God rules over all the earth then idolatry is just stupid. I hadn't thought about the significance of the emphasis on idolatry in these chapters before, and that just seemed to me to be at least some evidence against the predominant scholarly view of this section of Isaiah.
I should say as a caveat that I don't agree with those who say that the mainstream view entails a denial of viewing this book as the word of God. God could easily have inspired later authors to collect Isaiah's materials together and to add some of their own material to the book, and thus the announcement at the beginning of Isaiah need not mean Isaiah wrote the whole book. You can even hold an inerrantist view of this book and still think the title doesn't apply to the second half, given the clear division that takes place, with four whole chapters of historical material separating the two. Proverbs clearly has different sections written by different people, which means the attribution to Solomon at the beginning can't apply to the whole book (and Solomon's sections even contain proverbs that are almost certainly collected from other ancient near eastern wisdom literature anyway). So I don't oppose this view because I think it's inconsistent with viewing the book as scripture or anything like that. I just don't think the arguments for this view merit going against the most natural way of taking the attribution of authorship.