I intend no doctrinal or sectarian endorsements when I say that the orthodox view is the view that Christians have accepted for most of their history. I am attempting, as fairly as I know how to, to present the facts from the perspective of an outsider who used to be an insider. I know what Christians tell me they believe. I know what I believed when I was a Christian, and I remember what other Christians at that time told me they believed. I also have read what various historians have said about what most Christians have always believed.
The orthodox view is that the gospels present a generally accurate account, safeguarded by divine inspiration, of the life and teachings of Jesus of Nazareth, of his death at the hands of Pontius Pilate, and of events witnessed by certain of his followers beginning on the third day after his death; that the book of Acts presents a generally reliable account of the beginnings of Christianity; and that the canonical epistles more or less accurately record the prevailing beliefs of first-century Christians.
According to this view, Jesus' followers had good reason to believe that God had raised him from the dead. The view has it that they had good reason to believe also, based on what he had told them and what they had seen him do, that he was the son of God and savior of the world, the messiah whose coming had been prophesied in Jewish scripture, and that all who believed these things would be forgiven of their sins and be granted eternal life.
In this scenario, memories of Jesus' ministry were accurately preserved and transmitted by oral tradition within the Christian community throughout the first century and into the second, and this collective memory served as a confirmation of the gospels when copies of those books were produced and distributed after their authors were no longer around to vouch for them. Likewise the epistles were validated by those who could attest to their consistency with what the Christian community had known from Day One about Jesus’ message.
In the orthodox view, no matter whether most of the New Testament books were written by those whose names were assigned by tradition, they were written by people who were as knowledgeable as the putative authors would have been.
That is the orthodox view. What I am calling the conventional view is shared by most non-Christian skeptics as well as many liberal Christians. It departs from the orthodox view by, among other things, rejecting assumptions about divine intervention, specifically the real occurrence of miracles.
In this scenario, Jesus of Nazareth was a charismatic rabbi who probably claimed no unique relationship with God but advocated an ascetic and socially conscious Judaism that emphasized God's paternal benevolence. For reasons no longer knowable, his followers came to believe soon after he died -- no one knows exactly how soon -- that he was divine and did not stay dead. Inspired by this belief, they began to spread certain teachings that they attributed to him.
The first Christians, in this view, might have had no intention of starting a new religion, and Jesus himself almost certainly had no such intention. However, within a few years the message had gotten distorted, by Paul among others, eventually to the point of incompatibility with its Jewish origin. The gospels, while preserving a core of Jesus' original teachings, incorporate the distortions as well, along with a substantial layer of biographical myth and legend. The oral traditions that became the New Testament, although originally based on stories told by Jesus' disciples, had no reliable connection with the facts of his life.
Both views accept a consensus among New Testament scholars that the gospels were written between the early 70s CE and sometime in the 90s, that Mark was first and John last, and that extant manuscripts are substantially similar to the original documents although with some material added by copyists or redactors. The conventional view is that the gospels represent an evolution in the Christian community's perception of Jesus, from Mark's man of exemplary righteousness and unique wisdom to John's incarnate deity.
The conventional view also holds that the gospels were not produced independently. From textual evidence it is inferred that the authors of Matthew and Luke, and to a lesser extent the author of John, based their work on Mark's gospel while adding material from an earlier document known as Q, of which no copies now exist. According to this view, Q was an early collection of oral traditions about Jesus' teachings.
The orthodox and conventional views both accept that Paul was the actual author of at least seven of the epistles bearing his name: I Thessalonians, both letters to the Corinthians, Philippians, Galatians, Romans, and Philemon. In the conventional view, all other New Testament writings are of uncertain or unknown authorship and generally of later date than tradition supposes.
In both views, the first Christians were a group of Jews who formed the first church in Jerusalem soon after Jesus' death and thereafter set out to inform the rest of the world about him and his teachings. The first leaders of that church were Peter, one of Jesus' original disciples, and James, who was called "the Lord’s brother" and for that reason is generally presumed to have been a sibling of Jesus.
In both views, Paul was a very early convert to the movement and would have been informed about Jesus' life and ministry by people who had known Jesus. Or at any rate, he had ample opportunity to learn about the religion's founder from people who had known the founder, whether or not he ever took actual advantage of that opportunity.