Historians, scholars and Christian apologists can only use what documents they have available to them. If they only have hearsay accounts without evidence then they haven't got history they have myth. Christian apologists interpolate, guess and use hearsay because there's no real evidence, but they use this (undetectable) information like it is encyclopedic reference work.
The problem for people who try to perpetrate a deception is the fact that archaeologists and scholars do want to know what is the truth.
Blind faith is surrender to ignorance, probably the safest and easiest route, because looking for the answers through the intellectual process is much more difficult. However, that's what we do when we want to know what is true and what is a fabrication, and unfortunately it is the truth that advances human understanding. Anyone willing to put out the effort can get the information, but the followers of religion don't want to find anything inconstant or false about what they already believe.
Contemporary historians or (historians living in that time period) have written the facts and dates about significant things that happened in the past, and studying these writings can prove what did or didn't happen, and what is or isn't forgeries by the church Fathers, the Shepherd of Hermas, the Epistle of Barnabas, the Didache or Teaching of the Twelve Apostles, and the Apostolic Canons and Constitutions, are all forgeries of the early Church Fathers.
There are numerous forged works attributed to many of the Fathers of the early church, listed under the word Pseudo, or false. The Apostles Creed forged by the Fathers several centuries after the Apostles. The Creed is the work of twelve separate writers. This is how you know if something is actual history or a myth. There are historians that never wrote one word about Jesus that lived in the same place and time
Most Bibles when introducing the Gospels, as well as other writings that are contained in the canon, inform that the authors are anonymous and unknown. David Ulansey book on Mithraism, "The Origins of the Mithraic Mysteries", in which he convincingly shows that Mithraism originated in the city of Tarsus in Cilicia. That is where Paul of Tarsus came from. This is pretty good evidence Paul's beliefs came from Mithraism, which had many practices exactly like Christianity. Paul never cites the Gospels because the Gospels come much later. You can prove that by reading the Bible and you will find that Paul never refers to them.
In the Old Testament there are books mentioned that can not be found in the Bible, like the book of Jashar, mentioned in Joshua 10:13. That's not the only one, there are many. That fact certainly does indicate that there are missing Gospels, and this means the Gospels are not very likely genuine or authentic. "The Christ: A Critical Review and Analysis of the Evidence of His Existence" backs up no historian from his era wrote a single word about the Jesus. Also there is an abundance of scholarly work on this subject.
Look at the Gospel of Mark: he knows nothing of the virgin birth, or the Sermon on the Mount, of the Lord's prayer, or of other important facts of the supposed life of Christ. Matthew and Luke copied Mark and then later on someone added this stuff. The names associated with the gospels are only titles nobody knows who wrote them.
Matthew 5:1, 6:9-13 and 7:28 - Jesus delivered the Lord's Prayer during the Sermon on the Mount before the multitudes. Luke 11:1-4 he delivered it before the disciples alone, and not as part of the Sermon on the Mount. But the Dead Sea Scrolls prove that the Sermon on the Mount and The Lords Prayer existed hundreds of years before the supposed life of Jesus.
Erasmus, four hundred years ago, said the Gospels were originally written in Greek. The Gospel of John is largely composed of the speculations of Greek philosophy.
Matthew 2:1 says Jesus was born during the reign of Herod the Great, but Luke 2:2 says Jesus was born during the first census in Israel, while Quirinius was governor of Syria. Herod died in March of 4 BC and the census took place in 6 and 7 AD, about 10 years after Herod's death. Luke says this was the first census that took place under Quirinius after Herod's kingdom had been divided between his three sons in 4 B.C. (but the census was in 7AD, about 10 yrs after Herods death) The Jewish historian Josephus recorded that Herod the Great died in 4 BC. Josephus (Jewish Historian) says that Varus was governor of Syria at Herod's death and Varus was governor in 4 B.C. Historians that lived at the time didn't record Herod killing all babies up to two years old in Bethlehem either.
All documents about Jesus came well after the life of the alleged Jesus from either: unknown authors, people who had never met an earthly Jesus, or from fraudulent, mythical or allegorical writings.
"Canaanite Myth and Hebrew Epic" by Frank Cross (Cambridge Harvard University Press) the book has the history of religion of Israel compared to Ugaritic texts. Much of the Old Testaments and the religion was purloined from the Canaanite's religion.
The Nag Hammadi texts contained fifty-two books that were not approved as gospel called "heretical" books written in Coptic script which include gospels of Philip, James, Thomas, John and others. Archeologists have dated them at around 350-400 C.E. They are only copies from previous copies. None of the original texts exist. Scholars date these books as no later than 120-150 C.E. Others have put it closer to 140 C.E. The Judas gospel, a copy written in Coptic, dates to around the third to the fourth century. The original Greek version probably dates to between 130 and 170 C.E., around the same time as the Nag Hammadi texts. Gnostic texts could only have its unknown authors writing well after the alleged life of Jesus, they cannot serve as historical evidence of Jesus anymore than the canonical versions. The Nag Hammadi texts are hearsay.
Simply determining the dates of the documents and the birth dates of the authors is one way of knowing if it is an eyewitness account. It doesn't matter what these people wrote about Jesus; an author who writes after the alleged happening and gives no detectable sources for his material can only give example of hearsay. All of these ancient writings about Jesus came from the circulation of myths and superstition, and that does not require facts or evidence. There is no evidence for Jesus or the gospel writers existence; belief in Jesus is belief in what ancient primitive people fantasized (stories) that were told about something that happened long after the event.
Christianity is a Gentile mission concocted by the Romans to assimilate the Jews and all other religions. It was the synchronization of pagan and Jewish religions.
There is no evidence that James and Paul had any relationship because they did not agree on the Jewish religion (not Christianity) Christianity became the official religion of the Roman Empire after the Temple at Jerusalem was destroyed and James (the head of the Jewish Temple at Jerusalem) was dead. Then Paul exalted a fictional Jesus above James once James was dead. Paul (with assistance of the Rome Empire) started spreading this Jewish/ Pagan gospel.
Josephus's writings provide a detailed list of the cities of Galilee but Nazareth is not mentioned in all his volumes of writing. None of the New Testament epistle writers ever mentions Nazareth or a Jesus of Nazareth even though most of the epistles appeared before the gospels. No one mentions Nazareth until 40 years after Jesus is dead because it didn't exist before St. Helena the mother of Constantine, went looking for the city of Nazareth, and she discovered there was no Nazareth to find. So, they named an existing city Nazareth to cover that fact up. But some apologists claim Nazareth wasn't mentioned before since it was just a tiny little village but (if nobody wrote about Nazareth) because it was too tiny, how do apologists know it was tiny? No one recorded it. The Gospels refer to Nazareth as a city and the historians of that period would have known about a city of Nazareth if that city existed.
There are no arguments about the authenticity among the experts or scholars. It is really a matter of finding the facts. I have only given you a fraction of the facts that I could give that discredits the genuine or authenticity of Christianity or any other religion. They all have the same flaws. That is why people who want to know what is real should read things by unbiased scholars. Read a historical account of the Council of Nicaea, convened by the Emperor Constantine or the history of the Roman Empire, but there are people who have read historical accounts or documents that dispute what they already believe is true, but the discrepancies just whiz over their heads like a helium filled balloon.