Isaiah was one of the 16 radical or writing prophets who spoke to the people of Israel during a difficult time in their history. During this time, the people rebelled against God, experienced disorder in their society, and were often overpowered by their enemies. Occasionally, under the leadership of good kings, they experienced spiritual renewal, enjoyed prosperity, peace, and tranquility. The book of Isaiah has 66 chapters. Traditionally, many people have believed that Isaiah was the sole author of the book. However, in the last couple of centuries, biblical scholars have determined that other unidentified writers were also involved in the writing of this book. Several major events, described in the book itself, took place over a period of 300 years or more. This is true for the period of time that transpired between chapters 39 and 40. The overarching theme of the book is salvation. Other themes include judgment, punishment, captivity, the fall of the nation, comfort, hope, holiness, and salvation through a coming redeemer. While the first 39 chapters deal primarily with messages of judgment and a call to repentance, the last 27 chapters are messages of forgiveness and hope. The book is divided into three parts. Chapters 1-39, called Proto-Isaiah, emphasized divine sovereignty and holiness, urging radical trust and faithfulness to the Lord, announcing judgment on sinful practices and failure to trust, and envisioning God's eventual redemption of Israel in visionary and messianic terms. Proto-Isaiah generally is known as First Isaiah. Chapters 40-55 reflect the spirit of a new day, a time when God gave new challenges to the people. God is declared as the Creator, Redeemer, Lord, and Sovereign over all creation and all people. God would redeem people from all nations who sought the Lord. God would give a mission to all servants, who, through their endeavors, suffering, or other hardships, labored diligently to bring a message of redemption to the world. Included also are specific messages promising the release of the exiles from captivity in Babylon. This section of the book is called Deutero-Isaiah or Second Isaiah. Chapters 56-66, known as Trito-Isaiah or Third Isaiah, reflect conditions after the return of the exiles (538-515 BCE) to rebuild Jerusalem and the difficult and political challenges of that generation. While Isaiah does not mention the return of the exiles or the rebuilding of the temple, that story is found in the books of Ezra and Nehemiah. Also in this section, Isaiah focuses on events that will come to pass in the future.