I figure, to be forewarned is to be forearmed. Here's the corresponding article in the Insight book. Highlighting added. Red text are my comments.
*** it-1 1221-3 Isaiah, Book of ***
Unity of Writership. Certain Bible critics in modern times have contended that the book of Isaiah was not all written by Isaiah. Some claim that chapters 40 through 66 were written by an unidentified person who lived about the time of the end of the Jews’ Babylonian exile. Other critics pare off additional portions of the book, theorizing that someone other than Isaiah must have written them. But the Bible itself does not agree with these contentions.
Inspired writers of the Christian Greek Scriptures credited both the material now designated chapters 1 to 39 and chapters 40 to 66 to “Isaiah the prophet.” They never intimated that there were two persons who bore this name or that the name of the writer of part of the book was unknown. (For examples compare Mt 3:3 and Mt 4:14-16 with Isa 40:3 and Isa 9:1, 2; also Joh 12:38-41 with Isa 53:1 and Isa 6:1, 10.) In addition to this, there are numerous other places where the Christian Greek Scripture writers specifically credit material quoted from the latter part of the book of Isaiah, not to an unidentified writer, but to “Isaiah the prophet.” (Compare Mt 12:17-21 with Isa 42:1-4; Ro 10:16 with Isa 53:1.) Jesus Christ himself, when he read from “the scroll of the prophet Isaiah” at the synagogue in Nazareth, was reading from Isaiah 61:1, 2.—Lu 4:17-19.
Furthermore, the Dead Sea Scroll of Isaiah (IQIs a , believed to have been copied toward the end of the second century B.C.E.) contains evidence that the copyist who penned it knew nothing of any supposed division in the prophecy at the close of chapter 39. He began the 40th chapter on the last line of the column of writing that contains chapter 39.
The entire book of Isaiah has been passed down through the centuries as a single work, not as two or more. The continuity from chapter 39 to chapter 40 is evident in what is recorded at Isaiah 39:6, 7, which is an obvious transition to what follows.
*Those who would credit the book to more than one writer do not feel that it was possible for Isaiah to have foretold nearly two centuries in advance that a ruler named Cyrus would liberate the exiled Jews; consequently they speculate that this was written at a later time, at least after Cyrus began his conquests. (Isa 44:28; 45:1) But they fail to grasp the import of this entire portion of the book, because the material specifically deals with foreknowledge, with the ability of God to tell in advance what would happen to his people. Nearly 200 years in advance this prophecy recorded the name of one not yet born who would conquer
Those who deny that Isaiah wrote chapters 40 through 66 usually, for like reasons, deny that he wrote chapter 13, concerning the fall of . Yet chapter 13 is introduced with the words: “The pronouncement against that Isaiah the son of Amoz saw in vision.” Obviously, this is the same “Isaiah the son of Amoz” whose name appears in the opening verse of chapter 11:1.
*Note that the Insight book assigns motive to these scholars. This is considered adequate dismissal to a JW.
