The Book of Mormon includes twenty-one nearly complete chapters from the book of Isaiah, along with excerpts from several others. According to Joseph Smith, these writings were preserved on the brass plates—a sacred record Nephi obtained from Laban, whom he killed during the family’s flight from Jerusalem (1 Nephi 4). Smith claimed that these plates contained the writings of many prophets, including Isaiah, and that they were brought to the Americas by Lehi’s family around 600 BCE.

However, modern scholars have noted that the inclusion of such large blocks of Isaiah—particularly chapters widely believed to have been written after Lehi’s departure (commonly referred to as Deutero-Isaiah)—raises significant questions. These passages often appear disconnected from the surrounding narrative, inserted in ways that feel thematically strained or tangential to the storyline. Their presence seems more like doctrinal exposition than organic storytelling.

What’s more, the contrast in literary quality is striking. The Isaiah chapters, drawn largely from the King James Bible, exhibit a poetic elegance and rhetorical power that sharply contrasts with the more awkward, pseudo-biblical English found in much of Joseph’s original narrative. This juxtaposition makes it easy for readers to distinguish between the majestic cadence of Isaiah and the 19th-century imitation of 17th-century scripture that characterizes much of the rest of the text.

The irony is that while these Isaiah insertions were likely intended to lend spiritual authority and prophetic weight to the Book of Mormon, they also serve as a literary watermark, revealing the unevenness of the text’s composition and the challenges of blending ancient scripture with modern invention.