Isaiah is presented as a prophet of Jerusalem in the eighth century BCE, active under several kings of Judah, whose call, the vision of the Lord high and lifted up, the seraphim, the coal that touches his lips, opens the sixth chapter of the book that bears his name. The historical prophet spoke into the crises of Assyrian power, counselling trust in God amid the threats to Judah.
But the book of Isaiah, one of the longest and most influential in the Hebrew Bible, is understood by most scholars to be the work of more than one hand across more than two centuries. First Isaiah (chapters 1-39) contains the core of the eighth-century prophet's message. Deutero-Isaiah (chapters 40-55) presupposes a much later situation, the Babylonian exile and the rise of Cyrus of Persia, named as God's instrument, and is assigned to an anonymous prophet of the sixth century. Trito-Isaiah (chapters 56-66) addresses the community after the return.
The division rests on differences of historical setting, style and theology within the book, not on any external tradition, and it is among the assured results of modern biblical criticism, though the traditional view of a single author persists in some religious readings. The Great Isaiah Scroll from Qumran, a nearly complete copy a thousand years older than the previously oldest Hebrew manuscript, shows the book already in its full form by the second century BCE.