Three authors: Proto-Isaiah, Deutero-Isaiah, Trito-Isaiah. Presumably Isaiah (“proto-Isaiah”) wrote chapters 1–39, an anonymous author living during the exile (“deutero-Isaiah”) wrote 40–55, and another anonymous author living after the exile (“trito-Isaiah”) wrote 56–66. Scholars generally accept that the book of Isaiah was at least partially written by the prophet Isaiah, during the eighth century BC. However, there’sFortsätt läsa ”Who wrote Isaiah”