There are seven letters by Paul and it is accepted that they were written by Paul, but no one knows clearly who wrote the rest. A critical enquiry into all this started only in the 18th century as there was no critical study of the matter. The accepted authorship of Paul is regarding the Epistles to Romans, First to Corinthians, Second to Corinthians, to Philippians, to Galatians, to Thessalonians and to Philemon. Thus, even though some other epistles are attributed to authorship by Paul, many scholars do not accept that those Epistles were written by Paul.
This sort of argument has been going on since the beginning of enquiry into the subject. Regarding authorship of the Gospels, they are all viewed to be anonymous, though they are attributed to Matthew, Mark, Luke and John. This helps in the view to be correct. Thus one of the similarities between epistles and Gospels may be said to be on the question of authorship - no one knows who wrote them. At least there exist a lot of disputes regarding authorship. It is accepted that the Gospel and the first Epistle had been written by John the Evangelist or others who were close to him. It is however not clear whether the book of Revelation is a work of the same John or some other John. Thus it is clear that different parts of New Testament may have been written by the same author or his disciples, though there is no clear evidence either way.
Another problem arises from the large number of similarities between the Gospels of Matthew, Mark and Luke. This is the reason why they are called Synoptic Gospels which means that they have seen together. In comparison, Gospel according to John is materially different in both narrative and dialogue. This brings up a problem in both assigning of authorship as also the reasons for similarity. The question is whether each individual was relating the scenes from the life of Jesus that he had himself witnessed directly, or were the three Gospels the result of the work of one person and then written by others?
The other questions are regarding the duration of writing - short or long, and whether there were indeed separate persons writing the Gospels? The general view among critics is that the main source for the Gospels of Matthew and Luke are the Gospel of Mark and another common source, generally called Q. source-based up on Quelle in German which means source. The possibility of this is highlighted by the discovery of Nag Hammadi in Egypt in 1945. This discovery contained 52 books in Coptic which all date back to 350 to 400 AD. This contained gospels in the name of Thomas, Philip, James, John and others. These are all copies of the original Gospels. In many cases, the experts are arguing about dates of books where the original text has not been found. The suggested dates vary from 50 AD to third century AD.
At the same time, let us remember that the concept of New Testament came at the end of three centuries of the church. The procedure started with a collection of letters and gospels in the 2nd century that were viewed to be genuine by experts. These contained four Gospels and many of the Epistles of Paul. Some of the scholars of the 2nd century viewed all these to be equivalent to the scriptures that were written in Hebrew. There were also other books which were considered to be holy, but slowly pushed into New Testament apocrypha. The rules for New Testament as it stands now, was first started by St. Athanasius, the Bishop of Alexandria in 367. This ruling slowly gained more acceptance till it was universally recognized in 397. This is the basis of faith for Roman Catholic and Eastern Orthodox churches. They both believe in Bible and the apostolic tradition. Both of these have to be interpreted by the church.
At the same time, there are also newer versions of Christianity. Protestants believe that they have a tradition of faith, practice and interpretation so that they can think of them independently and not totally depend on tradition. Yet it is said that this authority comes from the Bible and this leaves their beliefs to argument at all times. At the same time, the open window permits the raising of many questions - whether Bible is infallible in doctrine, is wrong in historical and other statements, or even whether it has enough divine authority. At the same time, it is believed that Bible is inerrant, and there are both literal and other interpretations. Some even interpret the Bible in a manner that would not make it contradict presently established scientific facts.
There are many statements made by Jesus as noted in gospels, or made by Paul in Epistles that seem like commands yet they are not being observed by many. One of these is where Jesus tells to sell all that each individual has and give that to the poor so that the person can reach the Kingdom of Heaven, or the call by Paul to imitate Jesus in celibacy. Thus it can be seen that both Gospels and Epistles are to be guides to the action of followers of Christ. Sometimes the language is symbolic rather than realistic. An example is where Jesus commands his followers to eat his flesh and drink his blood. Thus even after accepting that gospels and epistles provide the guidelines for action by followers, interpretations provide for a broad range of teachings. The position now is that it is not an impediment for being a cannon authority even to state that Scripture contain mistakes, or that the authors had followed a line of thinking that was less enlightened. This permits them to change practices with impudence. These are leading to many contentious practices in churches of today - ordination of women, abortion being condemned as a social tragedy but not a personal sin or crime, homosexuality being a genetic propensity, and now even the ordination of gay men and lesbians. This is the extension of logic to absurdity, and one would feel that it is more religious to say that the canonical function to maintain the instructions in Gospels and epistles as our guideline for behavior be maintained.
At the same time, let us remember that the four Gospels which are the starting point of Christian religion are not written by Jews, nor written by any of the "Twelve Apostles" with Jesus, or had been in existence for at least a century after the Apostles were dead. The proofs on this are the writings by church authorities and Father Origen had written "And not four Gospels, but very many, out of which these we have chosen and delivered to the churches, we may perceive." The interesting point is why these four and only four were chosen when we know that many others were in existence? This is clear through the sayings of Irenaeus who died around 202. He clearly argued that there should not be more than four Gospels as there are four zones in the world that we live, four principal winds though the church is scattered all over the world and the pillar and ground of the church is the gospel.
It was fitting according to him that there were four pillars, breathing out immortality on every side and vivifying our flesh for the church. "The living creatures are quadriform, and the Gospel is quadriform, as is also the course followed by our Lord." Both of these statements are clearly emotional and can be said to be emotional outbursts, which can be accepted as they were not forms of God. The real reason is given by another authority and that there were four principal churches then and each had its own Gospel. Gospel by Matthew was used at Jerusalem, Mark at Rome, Luke at Antioch and John at Ephesus. Thus the real origin of both the Gospels and epistles are the same - they were written by individuals for the purpose of use by the church. They need have been apostles, but were religious men answering the call of duty.
Let us now summarize the points that we have been talking about. First is that both Gospels and Epistles are essential parts of New Testament. The difference is that Gospels are essentially the history of Jesus Christ and his sayings by another person, while Epistles are letters to junior churches regarding the administration of the church by an authority of the church. The origins of both are not clear but one can only say that they were written by individuals for the service of our Lord. What that means is that the names attached to them are not necessarily of the persons who wrote them. The canonical function is clear from…