Occasional time references scattered throughout the book indicate that Isaiah arranged his prophecies in a basically chronological order (cf. 6:1; 7:1; 14:28; 20:1; 36:1; 37:38). However, they are not completely chronological. More fundamentally, Isaiah arranged his prophecies as an anthology in harmony with a unifying principle. That organizing principle seems to be that God's people should view all of life in the light of God's reality and should therefore orient themselves to Him appropriately, namely, as His servants.
Isaiah built a huge mosaic out of his prophecies and used pre-exilic material to serve pre-exilic, exilic, post-exilic, and eschatological ends. It is not unreasonable to assume that after Isaiah had completed what we now have in chapters 1-39 he received new revelations from God along a different line that led him to adopt the somewhat different style that is characteristic of the last part of the book. The first part deals primarily with the threat of Assyria and the second (chs. 40-66) with that of Babylonia, with chapters 36-39 forming a transition. Chapters 1-5 are an introduction to the whole collection of messages. Chapters 6 and 53 are the key chapters because they provide the most concise answers to the great questions raised in the book. The book contains many extended doublets: repetition of the same truth in the same consecutive steps.
