The Gospel and The Reasons for writing

The Gospel according to Mark

Reasons for writing
I think that it is important for us to consider why Mark wrote his Gospel. What were his reasons for writing? There are two considerations that we need to keep in mind when pondering the reasons that compelled Mark to write his Gospel account.
Peter
One reason why Mark wrote his Gospel may have a lot to do with his connection with Peter. If Mark is indeed connected to Peter, as early church tradition tells us, then one reason for the composition of Mark's Gospel could well have been the desire to preserve Peter's testimony. As the chief disciple of the original twelve disciples, Peter was not just any disciple of Christ. In a very real sense, Peter was THE disciple. If Mark in fact is dependent upon Peter for his information, then the Gospel may very well have been written in order to preserve Peter's memories of Jesus for the church. This would be especially easy to understand if Mark wrote at a time immediately before or immediately after Peter's death.
Docetism
But it is also possible that Mark was written with some specific situation in view. This is very difficult to know for certain, but it is certainly worth our consideration.
There are several striking and distinctive aspects to Mark's description of Jesus in his Gospel. Jesus is portrayed in this Gospel with some very human characteristics. In Mark, we see Jesus angry on several occasions (e.g., Mk. 3:5). We also read in Mark that Jesus was unable to perform miracles when the appropriate conditions of faith were not present (e.g., Mk. 6:1-6). Mark also points out more than the other Gospels that Jesus was going to have to suffer in a way that seemed incompatible with his position as Son of God (8:33; 9:31).
In the early days of Christianity, many people found it difficult to balance the idea of Jesus' divinity with the fact that he was also fully human. And so in the early days, many people had the tendency to fall off into one of two extremes. Either they tended to think of Jesus as being fully human, but not really divine. Or they tended to think of Jesus as being fully divine, but not really human. In the earliest days, the more prominent tendency seemed to be this last inclination. There were many people who simply could not accept the idea that Jesus, who was fully God, could be fully human so as to suffer and die like an ordinary man. And so they suggested that the divine Christ only came into the human Jesus at his baptism, and that this divine Christ then left the human Jesus before the crucifixion. We call the people who held this view "docetists" because they believed that Jesus only "seemed" to be human. (The word "docetist" is derived from the Greek word doke/w (dokeo) which means, "to seem"). The writer of 1 John was concerned to correct this docetic viewpoint. It is very possible that Mark's Gospel may have had these people in mind, too. Thus, in order to combat those who were asserting that Jesus only "seemed" to be human (but was really not), it is possible that Mark emphasized the reality of Jesus' humanity. In this way, Mark may have depicted Jesus as being angry and as truly suffering and dying in order to demonstrate to people who denied Jesus' humanity that Jesus was not only fully divine but also fully human.
Let me reiterate that it is NOT certain that Mark was writing against a docetic view like this. But it is surely a possibility that we need to be aware of.

The Gospel according to Matthew

Reasons for writing
Matthew's Gospel seems to be very practical in its outlook. It is not only an attempt to describe and interpret the life and ministry of Jesus Christ, the Son of God. It also seems to be an attempt to organize the material about Jesus' life and teachings into a form that could be directly utilized in the continuing life of the church.
Thus, it would seem that Matthew wrote his Gospel like a teaching manual. This Gospel could be used to instruct new converts by giving them a basis for the Christian faith. It could also be used to demonstrate the continuity between Jesus Christ and the OT. Thus, if we had to characterize the reasons for the writing of Matthew's Gospel, we would have to look at the "instructional character" of this Gospel. Matthew probably wrote his Gospel in order to aid the church in its instructional needs. As I just said, Matthew is like a teaching manual. And so this is probably one of the main reasons why it was written.

The Gospel according to Luke

Reasons for writing
There are many different theories as to why Luke wrote his Gospel. As a matter of fact, this topic has attracted a lot of attention from commentators and scholars in recent years.
When we look at Luke's reasons for writing, though, we shouldn't forget that Luke himself tells us something about his purpose in writing the Gospel. In his prologue or introduction which is addressed to Theophilus, Luke says that he is writing, "so that you will know the full truth about everything which you have been taught" (1:4). Luke also tells Theophilus about how he went about his work. It is apparent that Luke took his work very seriously. He studied the accounts that were written by other people, and on the basis of these other accounts, Luke decided to write "an orderly account."
One reason for the writing of the Third Gospel, then, seems to be a keen interest in the historical facts. Luke did not just write stuff down because it made a good story. If we can believe his words at all, we see that he had a strong interest in discovering the FACTS about Jesus. This is not to say that he just wanted to write a biography of Jesus' life. Luke's purpose is also evangelistic: he wants Theophilus and his readers to achieve a better understanding of their Christian faith. But he suggests that the best way to help them gain a better understanding of their faith is to set out as much as could be known about the life and teaching of Jesus himself. In other words, while Luke's interest is not only historical, he understands that historical fact is very important. Luke understands that the Christian faith must be anchored to the facts of history if it is going to be persuasive for his Gentile Christian readers. And so one of the reasons why Luke writes is to present an orderly account of the historical FACTS about Jesus' life and teaching. For Luke, the historical data was considered to provide the strongest proof and foundation of the Christian belief that Jesus Christ truly was the Son of God.
As is true of all the Gospels, Luke's Gospel was also written for an evangelistic reason. Luke was certainly interested, maybe even more than the other Gospel writers, in historical fact. He even tells us himself that he thoroughly researched his material before he started writing. But while Luke may have been keenly concerned and intrigued by the historicity of the life and teaching of Jesus Christ, his interest in the historical truth of Jesus' life is still salvational and evangelical. Luke wants his readers to believe in Jesus Christ. This evangelical concern remains central to his purpose. And so we must not forget that a major reason for Luke's composition of his Gospel is evangelical.

The Gospel according to John
Reasons for Writing
There are two basic reasons that I would like to point out for the writing of the Fourth Gospel.
Evangelistic
You can't help but notice John's own stated purpose in 20:30-31:
"Jesus did many other miraculous signs in the presence of his disciples, which are not recorded in this book. But these are written that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name."
John's purpose is decidedly evangelistic--"that you may believe and may have life in his name."
Gnosticism and Docetism
It is also possible that the Gospel was written as a response to the growing influence of Gnosticism and Docetism. Docetism, as we have mentioned before, is the view that Jesus was fully God, but not fully human (i.e. Jesus only "appeared" to be human). John may have written his Gospel in an attempt to help believers distinguish the true Jesus from the Gnostic position. If this is true, though, then it must be one of the great ironies of history that this Gospel, which was perhaps written to combat Gnosticism, ended up being used by Gnosticism so much!