The first Christian writer we have, Paul the apostle who Christians believe was converted not long after Jesus rose from the dead, completely ignored the life of Jesus. Paul knew that the pagan world was rife with gods and holy men who were not real but mere myths that he needed to solidly ground Jesus in history and thus give his theology a more objective standard. He didn't. Because he could not. He gave the world another saviour like Hercules who was all based on hearsay.

Christians try to explain away his disinterest in Jesus as a man (which means his audience was just as disinterested!) by alleging that he had no need for the life story for the topics he chose. But he focused on morality and defending the faith so much that he would have had to use it.When writing to the Christians of Corinth, Paul says that we who knew Christ according to the flesh know him that way no more (2 Corinthians 5:16).

The famous German theologian, Rudolph Bultmann took Paul’s assertion as proof that the gospels were full of mythology, not lies but just fables intended to teach a religious or spiritual moral. He took it as evidence that Paul steered the Church in that direction and the culmination was the gospels which are absurd if taken as literally true. Bultmann believed Paul meant that Jesus was to be ignored as a historical person and now he was to be seen in symbolic and spiritual terms as explicated by mythology. Indeed, Paul goes further than that. He says his followers are ignoring and have ignored that Jesus of history whether there is a history available for him or not. They are not going to worry about him. Surely Jesus must have lived in recent times if the Corinthians are to forget his earthly life? Not necessarily. Paul does not want anybody to be curious about Jesus’ earthly life and the reason for that can only be this one: that there was no point for nothing can be known for definite if anything at all can be found out about it.
What supports Bultmann is what Paul said that if we once knew Jesus according to the flesh we don’t anymore. That can be interpreted as saying it is what Jesus does for us now in our souls for he is with us since his resurrection that matters and the past should be forgotten. When Paul showed no interest in Jesus’ earthly life and when he could be interpreted that way that is the way he should be interpreted. If Paul had meant that we don’t see Jesus as an ordinary man any more then why didn’t he write that? That would have been clearer. We know how many in Corinth wanted to forget that Jesus was a man so he would have been clear in case he would encourage them. So he did mean what Bultmann said he meant. Even if Jesus lived a mundane life, it would be good to investigate it if possible. But Paul thinks that Jesus’ life has been lost to history because God wants the focus on the resurrected Jesus and what he is doing for people and in their hearts now.
Paul said that we view no man according to the flesh for they are not in it any more being new creations of God which demands a complete break and forgetfulness of the past (5:17,18). He says Jesus is to be focused on what he is now as well and not on the past. But each person will have a different idea of how to do this so Paul is exalting the human imagination as a tool of learning the incomprehensible truths that God stands for. So the Christian is to create myths out of Jesus.
Paul’s assertion says nothing about when Jesus lived for all he is claiming is that the Jesus we know in our hearts is not an ordinary human being and to be forgotten as one. It is the story of what Jesus does in your soul now that matters not the story of the earthly Jesus.
It is interesting that Paul says we are forced to love Christ by the fact that if he died for us then we died with him. Many systems of belief at the time were sort of pantheistic with many people being believed to be the one deity and Paul often talks strongly in this pantheistic vein. There is no evidence for saying he thought we metaphorically perished with Christ. That makes it possible that the deity Jesus is really a collection of people who die and when the deity resurrects he comes back as one person. And it is more than possible – it is likely. You would expect Paul to be careful not to suggest deities that were archetypes of humans and one with them or some of them but he did not despite such semi-pantheism being a major fashion of the time.
Indeed, such an interpretation as the Christians have would be impossible. They say us dying with Christ means we stop our lives of sin when Jesus’ death takes them away by paying for them so that we metaphorically die with him. But to say we are forced to love Christ by dying with him metaphorically makes no sense. It is like saying you are forced to turn away from sin when you repent but that is a tautology. You are not forced by repentance to repent.
It is interesting that he also says we are compelled to love Christ because he died and rose so that we might not live for ourselves but for him. But how could you love a man just because he wants you to live for him and love him? You can if you are that man in some sense – this is the pantheistic element again. Paul’s Jesus was a pagan God not a historical person. He was a divine force and an archetype that was believed to manifest as several people. To pagans when a man died the horned God died for man was his manifestation and the man realises when he dies that he was not his own person at all but was one with the deity who was acting as if he was that person and other men. Silly? Yes but all religion is ridiculous.

Proof that there was nothing known about the earthly life of Jesus is in the fact that Paul wrote: “If there is anything worthy of praise, think on and weigh and take account of these things [fix your minds on them]. Practice what you have learned and received and heard and seen in me, and model your way of living on it, and the God of peace (of untroubled, undisturbed well-being) will be with you” (Philippians 4:8,9).

Paul would not have dared to put himself forward as a good example if there was a Jesus whose life they could have learned from for he knew to be wary of boasting and here he is really bombastic. Why put the messenger before the Son of God himself? Christians explain that Paul meant that they had to see how Jesus would live through him for they had never met Jesus. But Paul was still boasting. The Philippians had leaders who Paul could recommend as examples and who would have been better for they lived with the people and Paul didn’t. So Paul did not leave out Jesus because they didn’t see just for they didn’t see much of Paul either to know him very well. The correct picture we get from all this is that Paul though he tried to avoid bragging felt forced to do it here and in his pride he forgot to recommend the religious leaders of the Philippians and as for Jesus, the obvious good exemplar, nobody knew what his example was like for he was only known through apparitions. There was no known earthly Jesus to model your virtues on.
Bultmann was right.