I. Summary of Defence of the Isaianic authorship by Gleason Archer [Gleason Archer, the legendary professor of Old Testament at Trinity Evangelical Divinity School, Chicago (he modestly told me in 1984 that he only knew 28 languages although rumours were that he knew many more), wrote the following discussion as a supplement to his rebuttal of the critical arguments for source division of Isaiah 1-39 and Isaiah 40-66 based on “Alleged Differences in Theme and Subject Matter,” and “Alleged Differences in Language and Style.”]
Additional Proofs of the Genuineness of Isaiah 40–66
1. First of all it should be noted that Jesus ben Sirach (48:22–25) clearly assumes that Isaiah wrote chapters 40–66 of the book of Isaiah. E. J. Young notes, “The tradition of Isaianic authorship appears as early as Ecclesiasticus.
The Authorship of Isaiah: A Straight-Forward Biblical Defence by Dr. Leong Tien Fock, (PhD in Semitic Languages and Literatures)
Assessment of current scholarship, both critical and conservative
According to An Introduction to the Old Testament, an “evangelical” book that is slightly “liberal,” by Tremper Longman III and Raymond B. Dillard (2006: 309-10):
In many respects, contemporary critical opinion about Isaiah has recovered from the excesses that characterized scholarship in the late eighteenth and early nineteenth centuries. The consensus among critical scholars has moved in the direction of acknowledging much of what was dear to conservatives: that Isaiah is not the result of a haphazard accident and internally contradictory, but rather the book as a whole shows a unity of themes and motifs. The tenor of much of the debate has shifted from focus on dissecting the text to recover sources and settings to efforts to expound the coherence and unity of the text as it exists. Arguments from conservatives for unity of authorship based on common themes and vocabulary have now in large part been taken over and pressed into service as arguments for a redactional unity in the book [italics added].