The four works called the Gospels are really four records of one Gospel. However the Gospel is not to be thought as only limited to the accounts of Matthew, Mark, Luke and John. The Gospel is found through out the Bible and especially the rest of the New Testament.

However with the disappearance of the eye witnesses to the events surrounding the life of Christ, it was essential to have a written record of the events. Therefore God in his providence preserved such an account long before the first generation of witnesses died. Written documents were needed for instructing new converts, and for teaching the people, as well as for use in public worship.

Literary Style
The Gospel form of writing is unique to Christianity but it is no accident of literature. The Gospels owe their style and substance to the appearance of Christ. The Gospels could also be called Witness Documents. They are not a Biography of Jesus, but a proclamation of His life and message. In fact they give very few details of a biographical nature. They refrain from developing the personality traits of the Lord.

But even though the events of Jesus' life are arranged in a coherent sequence their prime interest is not chronological. They don't set out the chronological events of the life of Christ nor do any of the Gospels claim to be complete in all of the events of Christ's life. John 21:25; Luke 1:1-4

The Gospel writers all followed a principle of selectivity. They purposely passed over large areas of Jesus' life in order to concentrate on a few of His discourses, healing and parables. In fact the emphasis is upon the last week of His life, with Matthew giving one fifth of his Gospel to this period. Jesus could have done the events recorded in the Gospels in about 6 months and we know that He had a three year public ministry. The other events have been selectively omitted by the Holy Spirit.

Synoptic Gospels
Sometimes the word Synoptic is used with the Gospels. This word has Latin roots and comes from two words. Syn means the same, and optic means to see (i.e. Optical). It means that they see things the same. Thus the Gospel writers see Christ in the same manner. They take a common view of the life of Christ, particularly in the area of His Deity. John has not been considered a synoptic Gospel because it is not close enough in content and dependence on the other Gospels.

But having said this it cannot be denied that the Gospel writers each wrote from their own perspective and as independent witnesses. Matthew portrays Jesus as the Kingly Messiah to prove to the Jews that Jesus was the Messiah. It was apologetic in style. Mark Portrays Jesus as the wonder- worker, describing the works rather than the words of Jesus. It had a practical purpose. Luke portrays Jesus as the friend of sinners and outcasts. His is a social outlook, defining mans obligations to God and man. This leads to what is called the Synoptic Problem.

Synoptic Problem
The Synoptic Problem becomes apparent when you look at the similarities and differences of the three Gospels. Of Marks 661 verses only 31 have no parallel in either Matthew and Luke. There are 250 verses common to Matthew and Luke that have no parallel in Mark.

The Problem
If the three synoptic Gospels were written totally independent of each other, why do they resemble each other so clearly, even down to the exact words that are used in the original languages? An example of this is the story of the cleansing of the leper in Mark 1:40, Matthew 8:2; Luke 5:12.

Secondly if they have a literary relationship to each other how can they be three independent witnesses to the deeds and teachings of the Lord Jesus Christ. 

Proposed Solutions

Theory of Mutual Dependence
Originally St. Augustine said that Matthew was used by Mark and Luke to write their accounts of the Gospels. However it is accepted by most scholars today the Mark was the earliest writer. This theory would say that Mark was the first account therefore the other two writers were dependent upon Mark. However this would destroy the originality of Matthew and Luke. If the theory is true why was there such a difference in the order of events.

Theory of Documentary Hypothesis
This view states that both Matthew and Luke, independent of each other, made use of Mark for the narrative portion for their Gospels. For the discourse or sayings material Matthew and Luke used another document, which has been called the Sayings of Jesus. This document has never been found but invented to fit their theory. It is virtually impossible to recreate the Saying of Jesus document from the gospels of Matthew and Luke. To create hypothesis and speculation in the explanation of the similarities between the Gospels opens the flood gates to unverifiable guess work. 

Theory of Oral Tradition
This view relies upon the fact that personal observation, memorisation of Christ's teaching and verbal communication of that which was seen and heard was used to compose the Gospels. They argue, did not the Holy Spirit promise He would bring to the remembrance of the apostles all the words which Jesus had spoken. John 14:26 Now this certainly does support the similarities in the account however it does not justify overextending the theory of Oral Tradition. John 14:26 is not teaching that miracle memories would be given to the Gospel-writers, but rather God would use means to bring this about.

Eclectic View
Oral tradition should never be pitted against written sources in the issue of the Gospels. It is not an either or matter. Luke 1:1-4 recognises both oral and written narrative materials. Both elements were used in the composition of the Gospels. Each Gospel writer had their own purpose in mind and under the divine guidance of the Holy Spirit made the best use of the sources available. They took into consideration both eye witnesses and written sources to compose that which the Sprit of God wanted recorded.

Why Similarities
There are similarities in the Gospels because first and foremost it is the same Holy Spirit who inspired the writers and their message. The eye witnesses were also observing the same facts, and these facts were transmitted and recorded accurately. Also each of the Gospel writers had one another to consult and interview. However in all of the transcript the divine element was the controlling factor which gave it the reliability and accuracy. It can be relied upon as the sure Word of God.

Why Diferences?
One thing that must be remembered is that Jesus proclaimed the Gospel of the Kingdom in different places in different ways and He performed similar miracles and acts in different places. Also as in a witness of an accident you have testimony given from different perspectives so in the Eyewitness accounts of the Apostles you have different observations of the words and works of Jesus. God does not override their personality in the communication of his truth. Their personalities come through each writing. There are also differences because the information was communicated using different forms. (Eye witnesses, written, oral tradition, direct revelation of God.) Each Gospel writer had a different purpose for writing the Gospel and so was selective in the choice of material and events in order to fit the individual plan and purpose. This also was under the direction and guidance of the Holy Spirit. What was the same was the message of the Gospel of Jesus Christ.