My previous blog argues that it is reasonable to conclude that Matthew, Mark, Luke, and Acts were written early; that these New Testament documents were written during the lifetime of the eye-witnesses. Here is the link: http://natureandscripture.blogspot.com/2017/05/argument-for-early-dating-of-christian.html In order to make a reasonable argument that the New Testament documents are reliable, it will also be necessary to show two more details: 1. Outside corroboration of the contents and 2. Consistency of the message over time.
As for outside corroboration, there are at least 11 Non-Christian Sources that mention Jesus within 150 years of his life; many of these sources are anti-Christian who are attempting to explain away the events surrounding the resurrection. J. Warner Wallace has written about these 11 sources and what they say about Jesus: http://coldcasechristianity.com/2014/is-there-any-evidence-for-jesus-outside-the-bible/
Curiously, over the same time period, there are only 9 non-Christian literary sources that mention Tiberius Caesar! This number is debated, but the point is that the number of ancient sources for Jesus and the emperor Tiberius Caesar are similar. Most importantly, you can get almost all the facts about Jesus from these 11 non-Christian and hostile sources. We therefore have evidence from non-Christian sources, outside the Bible, to corroborate the story of Jesus.
Archeology is another outside source that corroborates the New Testament writings. Luke, for example, “displays intricate knowledge of local names, environmental conditions, customs, and circumstances that befit only an eyewitness contemporary of the time and events.” Luke goes to a lot of trouble to list places, dates, and names of people. By including historical people and events, Luke gives skeptics opportunities to refute what he wrote. If he were inventing a story, why include specifics that could be checked out historically? The accuracy of these historical specifics recorded in Luke continue to amaze historians. For example, all eleven historical figures named in the first three chapters of Luke’s gospel have been confirmed by non-Christian sources and/or archaeology.
In fact, the entire New Testament has been proven to be historically accurate. “The New Testament writers put historical crosshairs into their accounts by referencing real historical figures and their doings. All in all, there are at least thirty characters in the New Testament who have been confirmed historically by archaeology or non-Christian sources.”
A third way to check the reliability of the New Testament writers is to look at what the students of the eye-witnesses taught and wrote. If what the students wrote is the same as the teachers, then we can show that the story did not change or evolve as time passed. Here is an article, also by J. Warner Wallace, explaining this “chain of custody.” http://coldcasechristianity.com/2017/why-i-know-the-story-of-jesus-wasnt-changed-over-time/
In his book, Cold Case Christianity, Detective Wallace explains other similar chains from Peter to Eusebius and from Paul thru all the early bishops and papal leaders in Rome to the time of Justyn Martyr and Tatian. The conclusion is the same: the custodial sequences acknowledge the eye witness accounts existed, were treated as sacred scripture from a very early time, and were handed down with care from one generation to the next. The story of Jesus did not evolve, nor was miraculous theology added later.
The New Testament chain of custody preserved the primacy of and sacred importance of the eyewitness documents and delivered them faithfully to those who would later identify them publicly in the councils that established our present canon of Scripture. These councils did not create the canon or the current version of Jesus we know so well; they simply acknowledged the canon and description of Jesus that had been provided by the eyewitnesses.
At least 11 Non-Christian Sources mention Jesus within 150 years of his life. The chain of custody, which tracks the teachings of the original apostles through their students, shows that these teachings did not change or evolve. The historical accuracy of the New Testament writings is impeccable. The New Testament was written early, has not changed, and is corroborated by outside sources. It is reasonable to conclude that the New Testament is reliable.