Isaiah was written to demonstrate the turstworthiness of the Lord, and to establish that he does all things for his glory. Everything else is defined by how it relates to God as the center of reality. The book is addressed at multiple audiences, including Isaiah’s fellow countrymen in 735 BC, those living during the Assyrian invasion of Judah around 700 BC, and even 150 years later when Israel was in the Babylonian exile around 550 BC. The book also ends with messages for all times and all people under God’s covenant. Isaiah reveals a great deal about the coming messiah, including the well known passages about the Suffering Servant that the New Testament reveals as Jesus. There are many themes in Isaiah, but the main teaching of the book is that it is ultimately God who is guiding all of human history, and it is God who history revolves around; therefore we ought to repent of our sins, and put our trust in him through his messiah rather than worldly powers, because it is he who will have the final victory and bring judgment and justice to all mankind.