More than you ever wanted to know about deutero-Isaiah
Last week, I said: "I'm aware of nothing that prevents or prohibits an Orthodox Jew from accepting that the book of Isaiah had (at least) two authors who lived hundreds of years apart."
Granted, this isn't the Mainstream Jewish Understanding of the subject, but the MJU has been wrong before. [1, 2, 3] Besides, the MJU of science or history isn't religiously binding. You can go your own way, and think your own thoughts, and still be halachic. Often, you can even find legitimate Torah scholars who expressed ideas that better fit the facts as scientists or historians understand them.
Deutero-Isaiah is as good an example as any.
According to the MJU, the book of Isaiah was written by a prophet who lived at the end of the First Temple period. As has been noted from the time of the Ibn Ezra at least, the last half of his book(40-66) is written in a different style and speaks in detail of events that occured some 200 years after the prophet lived. No other book of prophesy is quite so precise about the future. Is it permitted for an Orthodox Jew to make these observations, and to conclude that Isaiah had two authors?
I say, yes.
My friend Fred has written a long and thorough post on the subject which supports me. After reading his outstanding discussion, including citations from scholars like the Ibn Ezra and the Shir, I can't understand why anyone would say deutero-Isaiah is treif. It may not be true -certainly you can argue against the critical evidence on its own terms-- but I don't see any theological grounds for opposing it.