The question of how many individuals wrote the book of Isaiah is an old one, but it is still frequently asked.

One Isaiah, Two Isaiah, Three Isaiah, Four?

The book of Isaiah clearly has two distinct halves – what is sometimes called “first Isaiah”(chapters 1-39), and  “second Isaiah” (chapters 40-66). These two halves have very different approaches and themes.

The first half of the book looks at judgment while the second half looks at redemption. The first section focuses on Judah and Assyria, while the second is about Jerusalem and Babylon. The second half of the book also appears to be set about two centuries after Isaiah lived and prophesied. The first half speaks of future captivity for the Jewish people, the second half speaks of their release – from what appears to be the perspective of that later date. There are also specific details which could not have been humanly known in Isaiah’s time. For example, the Persian king Cyrus is named 150 years before he lived (44:28; 45:1).

As a result of these facts, many claim that the second half of Isaiah cannot be ascribed to the same author.  Some scholars go one step further and divide Isaiah into three parts by citing differences between chapters 40-55 and chapters 56-66, and yet other scholars see indications of even more Isaiahs – other individuals who may have contributed later sections to many parts of the book. This last viewpoint is based largely on the fact that some ideas in Isaiah (such as the end of the age and the resurrection of the body mentioned in 26:19) are presumed to not have come into existence till much later, and while some sections of the book speak of the prophet in the first person (for example, chapters 6, 8), other sections such as chapters 7, 20, and 36-39 are stories about him, like those we see in the books of Kings – and so they are presumed to have been added by later writers.

Arguments for unity

On the other hand, there are numerous reasons why Isaiah can be viewed as the work of a single author.

Vocabulary and expressions:  Isaiah uses by far the largest Hebrew vocabulary in the Old Testament (almost 2,200 different words) and although there are subtle differences between the use of words in the two sections there are at least 25 words and expressions that are used nowhere in the Old Testament except in Isaiah, but which are used in both halves of the book.  For example, the expression “the Holy One of Israel” is rarely used in the rest of the Old Testament, but occurs 12 times in Isaiah 1-39 and 14 times in chapters 40-66, suggesting a single author.

Structure: The first half of Isaiah records his commission to preach condemnation (chapter 6), the second half records his commission to preach comfort (chapter 40). Both halves of the book of Isaiah begin with the old city of Jerusalem (1:1 and 40:2) and both close with God’s new city on Mount Zion (35:10 and 66:20). Structural parallels such as these suggest a unity in the work.

Argument from logic:  If the prophet could predict the coming of the Messiah in detail hundreds of years before that happened (chapters 42; 53; etc.), he could certainly have foreseen the return of the nation of Judah from eventual captivity, or the name of king Cyrus. This is no different from the  foretelling of Josiah’s name and reign three centuries before his birth (I Kings 13:1–2).

Manuscript Evidence: There is no known ancient manuscript of Isaiah, either in Hebrew or in Greek, which is divided in a manner indicating it was originally composed as two or more books. For example, the Isaiah scroll found among the Dead Sea Scrolls, and dating to the second century before Christ, has what we call chapter 40 beginning in the same column that contains what we call chapter 39. This is a strong early witness to the unity of Isaiah.

Evidence of the New Testament:  Jesus and the writers of the New Testament all speak of Isaiah as a single individual wherever they quote from the book. In John 12:37-41 Jesus quotes from both halves of Isaiah and attributes both quotes to the same author. Similarly, Matthew 3:3 and 4:14, Mark 1:2 and 7:6, Acts 8:30 and 28:25, and Romans 9:27 and 10:16 all quote Isaiah as a single person.

Conclusion
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While it is perfectly possible that Isaiah was edited in some details in the course of later biblical history – perhaps by later prophets – most of the differences between the major sections of the book can be explained by the possibility that Isaiah completed the first half of the book in the period between 740 BC and  686 BC., and the second section somewhat later. The opening of the second section of Isaiah “Comfort, comfort my people, says your God. Speak tenderly to Jerusalem, and proclaim to her that her hard service has been completed, that her sin has been paid for” would then show that the prophet was looking ahead, past the judgment that had occurred, with words of comfort for the new situation of the second half of the book.  

Most Christians know the story of the teacher of the law who asked Jesus, “Who is my Neighbor?”  This was the question that prompted Jesus to reply with the Parable of the Good Samaritan – showing that even our enemies are neighbors when it comes to the law of God.

But what if the teacher had asked the question in a slightly different way, saying, “Who is my Friend?”  Could the answer to that question also impact our understanding of the Way of Christianity?  We don’t have any indication in the New Testament of that question being asked of Jesus, but we do have Jesus’ answer to it, nevertheless.

In his Gospel, Matthew tells the story of Jesus’ betrayal in the Garden of Gethsemane. Judas Iscariot, the disciple turned traitor, had led a group of soldiers and other armed men to where he knew Christ would be in order to betray him for a cash reward.  As Judas approached Jesus in the dark of night and greeted him with a kiss in order to identify him to those who were to arrest him, Matthew records Jesus’ surprising  words:  “ ‘Do what you came for, friend.’ Then the men stepped forward, seized Jesus and arrested him” (Matthew 26:50).

Think about this. Jesus was not one to soften the truth. He was the one who called the Pharisees “whitened sepulchers” and a “brood of vipers” – to their faces.  But at the very moment of his betrayal , Jesus did not call Judas all the things we probably would have done. He did not call Judas “Traitor!” “Enemy!” “Back-Stabber!” – he did not even call him “False Friend!”  Amazingly, he just called him “friend.”

Now if we want to get technical, the word the Bible uses to record what Jesus called Judas was not philos, the Greek word usually translated “friend” and meaning “dear” in the sense of a close friend.  It uses the word hetairos meaning “friend” in the sense of a comrade, one who is a friend without necessarily having any affectionate relationship.  But he did call Judas by a word that means “friend” in the general sense (Matthew also uses the word in this sense in Matthew 20:13 and Matthew 22:12).

How do we apply his example?   The Old Testament gives us some clues.  Hebrew has a word, merea, which is very similar in meaning to the Greek hetairos – it also means friend in the sense of companion or comrade and it is found in Job’s words: “He who withholds kindness from a friend forsakes the fear of the Almighty” (Job 6:14). It is the same word that is used to tell us that after Job prayed for his “friends” (the individuals who had been haranguing him), God forgave them (Job 42:10).  

So if righteous Job prayed for the “friends” who mistreated him, and Christ could even call Judas “friend” as he betrayed him, can we learn a lesson from this? When we pray for our enemies (Matthew 5:44), do we pray grudgingly, with reservations, or do we pray for them as we would for a friend?