Furthermore, there is no manuscript evidence to show that the entire 66 chapters do not constitute a single whole. This has, recently, been strikingly illustrated by the discovery of a very ancient “Isaiah Scroll.” For, in it, Chapter 40 begins on the very last line of the column which contains 38.9-39.8. The last words on the one column are “cry unto her” and the first words on the next column are “that her warfare is accomplished.” Obviously, the scribe was not conscious of the alleged fact that an important change of situation, involving an entire change of authorship, begins with Chapter 40. If this manuscript dates from about the middle of the second century BC, it is an early witness in favor of the unity of the entire book. For it probably carries us back nearly to the time when the LXX version of the Prophets was made.
From: The Unity of Isaiah: A Study in Prophecy by Oswald T. Allis (Philipsburg: The Presbyterian and Reformed Publishing Company, 1950), p. 40.
Oswald T. Allis (1880-1973), the son of a noted Philadelphia surgeon, was a noted Reformed Old Testament theologian and author. He earned the Ph.D at the University of Berlin. He specialized in defending the authorial and literary integrity of the books of the Old Testament.