I've written a number of pieces about how to better understand God, and also how to better understand Jesus Christ as well as his God sent mission. I want to continue to produce a series on this top; some of these blog postings will be general thought pieces while others will include more detailed scriptural reference and quotations. Here I will start with a general observation.
The Apostles and the disciples, through their Gospels and Epistles, left a written record of precise things that Jesus said and did. Putting things in writing was not a commonplace activity in those times, even among scholars. There also was little concept of "writing a book for posterity" or for "teaching purposes." Too many people slip into thinking of the Gospels and Epistles that way, as if they were produced much as a book or newspaper column would be today (that they were written with both a targeted audience and with posterity in mind). But that is not how it was then, in the time of Jesus. Writing the Gospels and the Epistles only crossed the mind of the Apostles and disciples when there started to become a substantial number of far flung early Christians with some centers of gravity during times when travel was dangerous, time consuming, and the communities were in danger of martyrdom. I don't want to do a scholarly post here, but invite you to gain an overall perspective and flavor for what they wrote about Jesus, what he said and what he did.
The Gospels of St. Mark and St. Matthew are clearly written to record for a growing community of Christians the most essential events and components of Jesus' ministry. Again, do not confuse this with modern concepts of textbook, biography, self help book, or even purposes as we see in the Old Testament books, which is to codify God's law, record the visions of the prophets, and to preserve both wisdom and sacred teaching. What the Apostles and disciples were doing was "bearing witness." They were following the guidance, given by God to the ancient Israelites, about how to give truthful testimony in a public presence. 99.9% of the time in those days "bearing witness'' is given verbally. It is what someone would say to a group of people when bringing important news or engaging in a formal agreement or contract. As the community of early Christians came into being in the years immediately following the death, resurrection and ascension of Jesus into heaven, the Apostles and disciples realized they could not meet the demand in person for their "giving witness" in the synagogues and public squares. So St. Matthew and St. Mark wrote their Gospels, so that copies could be made and sent to places where they could not send an Apostle or disciple.
St. Luke's Gospel is the same in intention but with a different tone. His has detail of events regarding the Blessed Virgin Mary, for example, that could only have come directly from her telling. (The words she was inspired to say at the Visitation known as The Magnificat, for example). St. Luke's Gospel is the result of someone who "had some time to sit down and organize" some of the recollections of the Apostles, disciples and Mary, so there is a layer of detail that results in addition to his supporting the events and words of Jesus preserved by the Gospels of St. Matthew and St. Mark. These three Gospels, therefore, are very much similar in their purpose, which is to witness to events in a truthful and detailed way and to share that witness when the Apostles and disciples could not physically travel to a place that needed to hear the Gospel from them directly.
Likewise St. John gave his witness and preserved the telling of the truth of the sayings by Jesus and events in his life. But St. John differed from the other three Gospel writers in three crucial ways, and so his Gospel has a different "feel" and richer content in both details and tone. St. John was the only one of the Apostles not to have his life cut short by martyrdom. St. John lived to an extreme old age, around one hundred years. And St. John had responsibility for the care of the Blessed Virgin Mary for the length of time that she had remaining on the earth. St. John, therefore, was able to write much later than the first three Gospel writers and in a more musing and integrative way. He would have spent years in the company of the Blessed Virgin Mary. This does not mean what it would today, which is that he would "provide more detail" because remember, there was no concept of "biographies" or personage oriented textbooks. The Apostles and disciples wrote what they felt was necessary "in the field" at the time. While they of course had a sense of passing down the Gospel through the generations, again they were thinking in terms of fathers, sons, grandsons etc receiving the word and witness and passing that devotion on to their descendants. They were preserving the witness to be passed down, not "the book." There is no way that the Apostles and the first disciples would ever have thought about the existence some day of "the Bible." They wrote down their witness. However, very quickly as the early Church flourished, within the very earliest one to two hundred years after Christ the Church fathers rapidly saw the need to compile the authentic witnesses of the Apostles and disciples (especially as St. Paul gave such implied structure through his volume of works) and their continuing attachment to the word of God previously given, which is the Torah, the books of the Jewish people, which in time came to be called the Old Testament.
I go into this to invite you to see the Gospels and Epistles through the eyes of those who wrote and produced them, for it is that way that you better understand their truthfulness, their meaning, and their proper context. When you read something, especially if it is sacred literature and scripture, it is essential to understand the intent of the "author" (author is used advisedly because there is a writer who authors a book but the book is under direction of the Holy Spirit in general and recording real events in the life of Jesus Christ specifically). So it is always a co-authorship. Jesus said things and did things so that the Apostles and disciples would recall them and repeat them. So Jesus selected parables and so forth that he knew they could best witness and transmit. Jesus "thought ahead" for them by telling them things that they could understand and repeat in truthful witness. In modern book writing authors ask their subjects to "think back" over past events and relate them to the author who will sort, analyze and compile them. This is not how things were done in ancient times. Jesus told them parables and gave specific preachings (such as teaching the "Lord's Prayer" and the "Beatitudes") so that Jesus could "in advance" "shape" the form and content of the recorded word that is passed along to others. Secondly the Holy Spirit, who had arrived on Pentecost for those present in the room where they awaited to Mary, the Apostles and the disciples, guided the hands of those first writers of the words and events of Jesus so that they would have perfect discernment of what to include that was faithful, accurate and pleasing to God. Jesus told them, when he was there, to remember the words he said (often he would highlight words of particular importance). The Holy Spirit would ensure that they did and could discern what was of significance to record. Far from keeping "secret learning" to be "discovered by later generations," there was a double duty safety net of Jesus himself and the Holy Spirit to ensure that everything was included in the Gospels and Epistles. People of ancient times, most of whom could not read or write, had to rely on precise memory. The Apostles and disciples would have had scholars who were Christians who could aid in the writing and translation of their recollections and witness, but those were only "hands" and not "editors." The Apostles and disciples had received perfect formation of what to remember when it was actually said and done by Jesus in person, and then to recall and discern what to present within context of a written document by the Holy Spirit.
For example, St. Matthew's Gospel opens with the precise rendition of the lineage of Jesus by name of each ancestor back to King David. Remember that St. Matthew was one of the original twelve Apostles, so he would have had local access to the memories of the family of St. Joseph to record the name of each ancestor of Jesus. This is not something that, for example, Jesus made them all sit down and memorize the names of his grandparents, great grandparents etc. This is something that St. Matthew would realize in the course of his being one of the original Apostles that would be part of witnessing the fulfillment of the prophecies of the Messiah to come as being of the House of David and thus crucial testimony to provide. This is an example of the Holy Spirit inspiring St. Matthew to include data of tremendous theological importance. Likewise St. Luke is inspired to recognize the importance to record in his Gospel the words of the Blessed Virgin Mary, who in her turn was inspired by the Holy Spirit, to utter the prophetic Magnificat. The Holy Spirit ensured each writer would provide not only the structured information that Jesus himself provided but also the supporting context that those they sought to give the word to would appreciate and have to strengthen their faith and understanding of these events.
So I'll bring this installment of this topic to a close by summarizing my purpose. People need to drop secular modern day concepts of "authorship" or "a book" in order to understand what they are reading in the New Testament. The New Testament is comprised of written works by the first generation of those who knew and accompanied Jesus and the Apostles that exists in writing only because with the flourishing of Christianity from the first days after the death, resurrection and ascension of Jesus to the death of the last living Apostle, St. John, there was a need and an urging by the growing communities at long distances to have the witness of the Apostles and disciples delivered to them in writing if unable to do so in person. These are the words that the Apostles and disciples would have said in person to those they were evangelizing to had they been able to be in many places at all times. People who were able to go "into the field" urged them to put these witnesses in writing. We know this because St. Matthew's Gospel was immediately translated into the Greek. So the Gospels were the "outreach" in the form of writing what these earliest companions and witnesses to Christ would have said in person had they been there and been able to travel far and wide, live long and escape martyrdom. Since that was neither their calling (to evade martyrdom and lead long safe lives) nor the practical conditions of the time (St. James, for example, was martyred not so long after Jesus), they were compelled to put their witness into writing to reach those who might otherwise be deprived of it. Understanding that allows you to have a better appreciation for the accuracy and purpose of these books of the Bible themselves.
I hope that you all find this useful.
(By the way, the Pope has a great explanation of the Rosary as "the school of Mary" and the Magnificat at this link http://www.zenit.org/article-22771?l=english ).