Two Isaiahs Hypothesis — Steelmanned

The hypothesis that Isaiah 1–66 is the work of multiple authors, written across multiple centuries, was not invented in modern times — Ibn Ezra in the twelfth century already gestured toward it — but it was Bernhard Duhm's 1892 commentary Das Buch Jesaia that gave the proposal its definitive modern shape. This section presents the case as fairly as it can be put.

The argument has four pillars. First, setting: chapters 1–39 plainly address the eighth-century BC world of Assyrian threat under kings Uzziah, Jotham, Ahaz, and Hezekiah; chapters 40–55 plainly address an exilic-Babylonian audience; chapters 56–66 read most naturally against a post-exilic restoration setting. Second, named figures: Cyrus, the Persian king who would conquer Babylon and decree the return, is named in 44:28 and 45:1 — a generation and more after Isaiah ben Amoz's lifetime. The critical reading takes this as evidence the chapter was written closer to the events. Third, vocabulary and style: the characteristic phrases of 1–39 (e.g., the recurring 'in that day' formula, 'the LORD of hosts') shift in 40–55 (where 'Holy One of Israel' takes a new prominence) and shift again in 56–66. Fourth, theology: the rich monotheistic polemic against the gods of Babylon (40–48), the developed servant figure (42, 49, 50, 52–53), and the eschatological universalism of the closing chapters (60, 65–66) develop themes not equally distributed across the book.

Duhm's tripartite division — Proto-Isaiah (1–39), Deutero-Isaiah (40–55), Trito-Isaiah (56–66) — became the standard vocabulary of academic-critical Isaiah scholarship and remains so. The case is not frivolous. It is a coherent reading that takes the book's apparent shifts of setting and vocabulary as evidence of multiple authorship across centuries.

The rebuttal follows in the next section.