It is commonly assumed that the church and New Testament writers felt free to create stories and sayings for Jesus as they saw fit. They point out that many passages are likely to be products of the Church's faith rather than actual historical events. We will examine some arguments and reasons why we can safely conclude that the New Testament does not contain these created 'Gospel Fictions' or lies.
How could the authors of these supposed "pieces of historical fiction" expect to get them past the eyewitnesses? The eyewitnesses could act as a check against imaginations, exercise control over the developing tradition and examine doubtful statements concerning Jesus' ministry. There were a number of early disciples / eyewitness (hundreds, and even thousands). The early church did not grow up in isolation, in some corner, but in the full glare of publicity in the great cities of the Roman Empire. 
It was also not only friendly eyewitnesses that they had to deal with. They could not afford to risk inaccuracies and especially not any manipulation of the facts. The many hostile witnesses, who were also aware of the main facts surrounding the life of Jesus Christ, would at once expose these. In fact, one of the strong points of the preaching of the early followers of Jesus, was their confident appeal to the knowledge of their audience. They not only said, "We are witnesses of these things", but also, "As you yourselves know". (2 Peter 1:16 and Acts 2:22) [6 p. 53]
Certainly, they could have made things much easier on themselves by, for example, permitting sacrifices to the Emperor of Rome or perhaps making the difficult passages easier to understand! 
Much of what is in the Gospels is not relevant to the early church. If there are passages that were created and put on Jesus' lips, and were therefore products of the early church, why are there not teachings of Jesus on subjects critical to the early church? Such as circumcision, speaking in tongues, Jewish/Gentile unity, divorce of non-Christian spouses, women in the ministry. If the church felt free to invent Jesus' sayings, why not some sayings on these issues? 
The Fiction theories are necessary complicated as they demand an explanation
The church had a solid oral tradition (and this is even stronger when considering the likely possibility that Jesus' sayings were also written somewhere), how did anyone get away with creating new sayings of Jesus? Anything not agreeing with what Jesus said would have been rejected. 
Examples include accounts such as the competition of the apostles for high places in the kingdom, their flight after Jesus' arrest and Peter's denial of Jesus. [6 p. 53]
Examples include: the failure of Christ to work miracles in Galilee, the references of some auditors to His possible insanity, His confessions of ignorance as to the future, His moments of bitterness, and His despairing cry on the cross. No one reading these scenes can doubt the reality of the figure behind them.
Paul (in 1 Corinthians 7:10, 12) indicates that a difference was recognized between the words of Jesus and his own words. If he could simply add to what God said, why did he feel the need to clarify the difference?
For example, consider the analogy of how easily World War II was remembered twenty to thirty years afterward. If someone suggested some seriously distorted version of the events of those days, no one would be fooled.
Also, consider the example of the release of Nelson Mandela. Suppose that, thirty years after his release from prison, a non-fiction best-seller portrayed a thoroughly consistent picture of Nelson Mandela having never left prison, but rather dying in his cell before he was released. Although most of us did not know him personally, we would certainly know enough to contribute to a rebuttal.
Lies are always told for some selfish advantage. They did not benefit at all by claiming that their Master was God incarnate. They were ostracized, criticized, rejected, persecuted, and in many cases martyred. They were hated, scorned, persecuted, excommunicated, imprisoned, tortured, exiled, crucified, boiled alive, roasted, beheaded, disemboweled and fed to lions. Nor did they make lots of money by making the claims that they did. [1 p.186]
The historical fact is that no follower of Jesus ever confessed, freely or under pressure, bribe or even torture, that their accounts of Jesus were a lie, a deliberate deception. [1 p. 185]
They were honest, simple, common peasants, not cunning, conniving liars. Their words and deeds proved their sincerity. They willingly died for their "conspiracy". Nothing proves sincerity like martyrdom. [1 p. 185]
There is great accuracy used in describing events, places, and people (as confirmed by archaeology). 
"Simply let your 'Yes' be 'Yes', and your 'No', 'No'
" - Jesus (Matthew 5:37)
What book presents a higher standard of love and morality than the New Testament? For example, Jesus' "Sermon On The Mount" (Matthew 5-7) and Paul's "Discourse On Love" (1 Corinthians 13)
There is only speculation. To state that they writers of the New Testament lied, we must argue from silence - this is an incredibly weak argument. To raise the point that they lied as a mere possibility does not constitute advancing evidence for the speculation. 
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