Deutero-Isaiah (or “Second Isaiah”). A section of the biblical book of Isaiah variously identified by modern scholars as Isa 40–55 or Isa 40–66.

The three-author view subdivides the book of Isaiah into three units, each written by a different author:

• First Isaiah = Isa 1–39

• Second Isaiah = Isa 40–55, calling this section Deutero-Isaiah

• Third Isaiah = Isa 56–66

The two-author view limits Isaiah to two divisions:

• First Isaiah = Isa 1–39

• Second Isaiah = Isa 40–66, calling this section Deutero-Isaiah

Thus, at times scholars use Deutero-Isaiah synonymously with Second Isaiah (with both meaning Isa 40–66), while other scholars use the term to refer only to Isa 40–55. Most scholars use the terms First Isaiah, Deutero-Isaiah (or Second Isaiah), and Third Isaiah to refer to the authors of sections of Isaiah, but at times the terms are also used just to refer to the major literary sections without any implication of a multi-authorship viewpoint.

(There are also additional theories regarding the division and outline of Isaiah. For further details on these viewpoints, see these articles: Isaiah, Book of; Isaiah, Book of, Critical Issues.)