Few books have had so profound an impact on Judeo-Christian religious thought as Isaiah. It was once assumed by believers that the book was the unified work of a sole author, an eighth-century BC prophet named Isaiah who lived in the Kingdom of Judah. This view is still popular among the Christian and Jewish laity. But the true authorship of Isaiah has been the subject of considerable controversy.

The first to challenge the unity of Isaiah came from Jewish writer Moses Ibn Gekatilla in the second century AD. Modern critical scholarship of the book of Isaiah, however, didn’t begin for another 1,600 years. In 1789, Johann Doederlein argued that chapters 40-66 of Isaiah were actually the work of a post-exilic author—the so-called ‘Deutero (Second) Isaiah.’

Doederlein’s theory that there were at least two authors of the book of Isaiah is now held as a truism by the majority of Bible scholars. (Some posit a ‘Trito (Third) Isaiah’ who wrote chapters 56-66.) I won’t review all of the reasons why scholars reject the unity of Isaiah, but it’s important to briefly discuss a few.

For one, the author of the later chapters (40-66) explicitly reference historical events like the reign of Cyrus (559 BC-530 BC) that happened centuries after Isaiah’s death. This may seem to presuppose that Isaiah was not a prophet who could foresee the future, but the argument is more sophisticated than that. The issue is not that future events are mentioned per se, but how they’re mentioned. Cyrus and his Persian empire are discussed in a way that would’ve been incomprehensible to Isaiah’s contemporaries. And as such, Dr. Avraham Gileadi, an LDS Isaiah scholar, concluded that Isaiah’s prophecies weren’t intended for an eighth-century audience; they don’t foretell the coming of the Messiah or the end of Jewish captivity. Instead, they are meant to warn us modern readers of the coming Apocalypse.

There are literary and theological evidences that the book of Isaiah has multiple authors, as well. Despite coherent motifs throughout all of Isaiah, chapters 40-66 are distinct enough in both style and content that they are attributed to Second and Third Isaiah. The earlier chapters, for instance, are sharp and succinct, whereas the later ones exhibit an almost Psalm-like prose. Chapters 40-66 also introduce a number of theological themes absent in the rest of Isaiah, including: God’s restoration of a destroyed Jerusalem, divine creation, and the role of the ‘suffering servant’.

I’m sure my discussion of Isaiah is tedious if you’re not interested in higher Biblical criticism. But if you are LDS, you ought to take an interest in this. Mormon author Duane S. Crowther explains why, in his book How to Understand the Book of Isaiah:

The problem of the authorship of the book of Isaiah is of major importance to Latter-day Saints because it calls into question the divine origin of the Book of Mormon. The Book of Mormon quotes numerous passages from Isaiah which were found within the brass plates brought to the Americas by Lehi about 600 B.C. Many of the passages it quotes are from the passages Bible scholars assign to second and third Isaiahs [chapters 48-52 are quoted in the Book of Mormon], which according to their theories, were written long after 600 B.C.

If the theories of the Bible scholars are correct, then the Book of Mormon could not be quoting from the brass plates, and it is a false, or forged book of scripture.

To rescue the Book of Mormon from this anachronism, Mormons must disagree with the scholarly consensus regarding Isaiah’s authorship. It is of course possible that the consensus is wrong, but it is unlikely given the extent of agreement.

Dr. Walter Brueggeman notes that his fellow Bible scholars are of the “nearly unanimous” opinion that the book of Isaiah has multiple authors. Even Marc Schindler, writing for the Mormon apologetic website FAIR LDS, admits that “the Deutero-Isaiah theory is today accepted almost without question by most Jewish and Christian scholars.”

Here is a sampling of what preeminent Bible guides say about Isaiah’s authorship:

One of the success stories of the historical-critical method of biblical study has been to establish that the 66 chapters of the book come from a variety of backgrounds, and the custom has been to treat chs. 40-66 independently of the earlier part of the book. … [I]t might seem perversely old-fashioned to go back to treating the whole book as a unity. (The Oxford Bible Commentary, 2001)

The book of Isaiah was not written by one person at one time and in one place; rather, it was the product of a long and complex history. (Eerdmans Commentary of the Bible, 2003)

The bulk of the book [of Isaiah] was … probably composed more than a century after the lifetime of Isaiah. (The Oxford Companion to the Bible, 1993)

Christian tradition, like Jewish tradition, long-regarded the entire book as the work of a single prophet, Isaiah of Jerusalem. Critical scholarship, however, has taught us to distinguish First Isaiah (chs. 1-39), Second Isaiah (chs. 40-55), and Third Isaiah (chs. 56-66). (The Collegeville Bible Commentary, 1989)

The distinction between First Isaiah and Second Isaiah is so widely accepted in modern scholarship that the argument against it need not be examined at length. The distinction between Second Isaiah and Third Isaiah is almost as widely accepted … (The Anchor Bible: Second Isaiah, 1969)

Dissenting scholars are often committed to the unity of Isaiah because of their religious beliefs. Fundamentalist Christians have been the principal apologists for the unity of Isaiah, but Mormons like the aforementioned Dr. Gileadi have also come to its defense, and for good reason—at stake is the Book of Mormon’s historical integrity. Again, the brass plates could not have included Second Isaiah as it was not written until many decades after Lehi and his family left Jerusalem for the Americas.