Liberal scholars maintain that the book of Isaiah, the longest prophetic book in the Bible, contains the oracles of two, or even possibly three, prophets. The basis of the liberal argument rests on the difference in interest and content which is noticed from chapter 40 onwards. A different historical period is indicated with reference to Cyrus, ruler of Persia, who attacked and defeated Babylon in 539 B.C.

Conservative scholars maintain that one prophet, Isaiah of Jerusalem, is the source of the oracles of the whole book. It is maintained that he would have been able to speak to a future generation of Jews, during the Exilic period, as well as to his own generation.

The arguments for each position are very complex and reference should be made to commentaries which discuss them. For the purposes of our study, we shall look at the content of the selected chapters from the book of Isaiah but not go into the problems of authorship.