I’m doing a paper on Isaiah. Do you believe it is written by one author, two, or more…?
Many scholars claim that the prophet Isaiah wrote Isaiah 1-39 and that another author influenced by Isaiah wrote “deuteroisaiah” which would be Ch 40-66. They base this claim on supposed and sudden differences in subject, language and writing style. Also, there is a prophecy of Cyrus that some believe is too specific to have been made before the career of the emperor who freed Judah from Babylon. I do not agree with this claim, but will admit that it cannot be disproved. I probably am biased, but I have read more than one commentary on this and find the argument for two authors to be weak. The theme of Isaiah is clear and the two parts have identical themes the best I can tell. As for different styles, it is possible that Isaiah wrote at different times in his life. You can pick up any commentary of Isaiah and the author will discuss the two views. I do not think that the inspiration of the Bible is at stake in any case, as the inspiration of Isaiah 40, Isaiah 42, 52 and 53 are well established based, for example on the rather obvious prophecies of the Messiah. In fact, if anything, the evidence for inspiration for Ch 40-66 might be even stronger than 1-39. In conclusion, I lean toward the conclusion that there is a single author of Isaiah, but do not believe that it is completely unreasonable to propose two authors.