Edited last paragraph re Mark and Basilides ca 6 hours after original.
As to why a gospel was written about a “mythical” Jesus, here is a take by Paul Louis Couchoud from the 1920′s and published in English in 1939 as The Creation of Christ. (For other thoughts on this theme see discussion comments here.)
Couchoud attributes the first gospel to Marcion.
To make sense of this one must understand that Couchoud dates the letters of Clement of Rome and Ignatius to around 150 c.e. One recalls here the more recent ideas about the Ignatian letters by Roger Parvus. This leaves us with the common observation that “the half century from 70 to 120 is the most obscure period in the history of Christianity” (p. 110).
Couchoud argues that before that gap there was Paul, Jerusalem apostles and prophets. They all lay claim to visions of Christ. The Book of Revelation (dated prior to 70 and the fall of Jerusalem) is the outcome of a prophetic vision of one who is starkly opposed to Paul’s theology and visions. “Paul alone understood that the Son thus revealed was a crucified God.” (p. 132)
Couchoud relies heavily on Harnack’s interpretation of Marcion, an interpretation that has more recently met a trenchant challenge with Sebastian Moll’s The Arch-Heretic Marcion (2010). Moll says Harnack was anachronistically trying to make Marcion too much like an ideal Protestant reformer. But in this post I will let Couchoud have his say from his perspective in the early twentieth century.
Whereas many (including myself) have attempted to argue that the gospel narrative was an indirect response to the crisis of the first Jewish war that witnessed the destruction of the Temple in 70 ce, Couchoud places more emphasis on the events of the second Jewish war — the Bar Kochba rebellion (Bar Kochba being hailed as a Jewish Christ and being responsible for persecutions of Christians) and its suppression by Hadrian who erected a pagan temple on the site of the old in the early and mid 130s.
So of what had Christianity consisted up to this time? Couchoud considers how the Christian scene looked to Marcion:
The true God, remote from this world, remained unknown to men and to their creator. To Paul, at last, he revealed his son Jesus. True that Peter, James, John, and the Twelve had also received this revelation, but they had been unable to understand it, so blinded were they by Judaism. Paul alone understood and realized that the Son thus revealed was a crucified God. Since that day, for more than a century, Jesus had been manifest to the world, thanks to God and to his wisdom. Thousands of sinners had been drawn to him, and their sins, by his grace, had been remitted. His prophets had been granted many a vision, many a precept, and many a parable. By the hands of exorcists he had wrought many a cure, and the hour was at hand when, after the Antichrist, the Jewish Messiah, should have attempted once more to deceive them, he should come once again, in his glory this time, to assemble his faithful and to save the elect. How might the good news by told? (pp. 132-133)
Couchoud follows Harnack in believing that Marcion rejected completely the Jewish scriptures. This left a void in the readings and written documents to guide his churches. Paul’s writings were a powerful replacement of the Prophets, but something more was deemed useful. Couchoud’s thesis follows:
Marcion therefore needed to show that the apparition of Jesus was recent, and had nothing to do with what had been predicted or revealed in the old scriptures of the Jews, but was a new thing. The manifestation of Jesus was a terrestrial fact; therefore the crucifixion must also be a terrestrial event.
This idea was to have far-reaching consequences . . . . The populace straightway took it to heart. Novices of little instruction must have heard of it, Greeks of artistic bent, who took the theological data as a dramatized story. Thus there might come to the ears of some Roman magistrate obscure whisperings as the mystery of Christ Crucified. (p. 133)
The Roman magistrate Couchoud is thinking of is the one who wrote the earliest evidence we have of the belief that Pontius Pilate and not Powers of Evil was responsible for the crucifixion of Jesus — Tacitus. The governor Pliny before him (ca 111 ce) has no notion that Christ was a real person according to his account to the emperor after questioning Christians. In Tacitus (ca 117 ce) we read of Nero scapegoating the Christians for the fire of Rome.
Couchoud believes that Tacitus must have picked up his account of Christian beliefs from the time of his proconsulship in the province of Asia. Roman Christians, says Couchoud judging from the Roman Christian writing of Hermas, “were far from thinking of Jesus as a historical person”. What Tacitus says about Christian beliefs more likely derived from the Marcionites. He speaks of Christians being named after “Chrestus” (not “Christos”), meaning “Good”, a term used by Marcionites for both Jesus and God. Pontius Pilate was first introduced into the narrative by the Marcionites, says Couchoud.
Couchoud thinks Pontius Pilate was selected as the one responsible for the crucifixion of Jesus because he was found to be the governor, and a suitably cruel one at that, at the time of John the Baptist according to the works of Josephus.
Marcion accepted enthusiastically this popular, pagan idea of Christ’s death; its simplicity appealed to him. It was looked upon as an accomplished event, and was not hampered with a baggage of visions, interpretations, gnoses, and what not. It was eminently readable and, read aloud in the churches, would arouse more fervid faith than the most ebullient prophecy. The manifestation of God, extraneous to the world, could be told in the form of a brief tale of Jesus on earth, concluding with his death on the cross, the sacrifice for the salvation of mankind, which St. Paul considered the essential and lasting act of Christ. (pp. 134-135)
So, once the cross of Jesus was planted on earth, once the name of Pontius Pilate had been discovered, it was not long before the details of a life were filled out.
Each church brought its scrap of good news; here all recalled a prophecy, there a parable, formerly inspired by the Spirit of Jesus, and now ascribed to Jesus himself. The work of Jesus remained what it had ever been — to call the sinners, cure souls, save the lost, preach the doctrine of the cross and love.
And what of the other apostles who had had visions of Jesus?
To clear the way for this new step it was necessary to show that the earlier apostles had ill understood their revelation, that they had been unintelligent, carnal, and cowardly, that Jesus had reprimanded them and had given them his approval of Paul’s teaching.
Visionaries had “seen” the investiture of the heavenly Christ. Paul had interposed the crucifixion before this investiture. To fill out an earthly life of Jesus it was only natural to set it in the period prior to the crucifixion.
A Mandean Clue?
Couchoud pauses to point out “a curious passage which seems to be an echo of John the Baptist announcing the coming of the Man from Heaven in John’s [John the Baptist's] time, the time of Pontius Pilate. In the Book of Enoch Enoch himself is carried up to heaven and becomes the Son of Man who is enthroned beside God. In this Mandean text (Ginza) the proclaimed Man from Heaven is the angel of Enoch called Enosh-Uthra.
Enosh-Uthra comes and makes his way to Jerusalem,
Garbed in a cloak of cloud.
He walks clad seemingly in a body,
But he has no raiment of flesh.
Wrath and vengeance are not in him.
He comes in the years of Pilatus, king of the world.
Enosh-Uthra comes down to earth
With the power of the King of Light.
He heals teh sick, causes the blind to see,
Cleanses the leprous, makes the lame to walk,
And those who drag themselves along the ground to arise,
Gives hearing to the deaf, and life to the dead.
He finds his faithful from among the Jews.
He shews them this:
There is Death and there is Life;
There is Darkness and there is Light;
There is Error and there is Truth.
He converted the Jews in the name of the High God of Light.
Three hundred and sixty prophets went up out of Jerusalem.
They bear witness to the Name of the Lord of Greatness.
Enosh-Uthra rises into the heights
And takes his place at the side of Mshunné-Kushat.
This Mandean text, says Couchoud, belongs to an “ancient line of ideas which goes back directly to the Book of Enoch.” In place of the cloud of heaven that wrapped the Son of Man in the Book of Daniel, here the Son of Man is wrapped in a cloud of flesh — an apparent body for the angel of Enoch. For the Marcionites such a one was in fact Jesus.
The Gospel of Marcion
Couchoud thinks that Marcion’s idea for a gospel narrative of a life of Jesus on earth was completed in 132 ce. In accord with Paul’s teaching, his Jesus only appeared to be a flesh and blood body. Marcion begins his gospel with Jesus descending directly from heaven to begin preaching in Capernaum — that is, “at the borders of Zebulun and Naphthali — on the seashore, where, said Isaiah, the Hebrew Christ was expected. That was why many, including even his first apostles, mistook him for the [Hebrew] Messiah. Despite his ancient name of the Christ, he was a new Deity.” (p. 140).
There was little narrative flow to this first gospel. It was later to be picked up by “Luke” and expanded and “catholicized” by incorporating strands from other gospels into it. But the first to respond to this gospel was “Mark” who has been associated with a gnostic form of Christianity owing its ideas to Basilides — though Couchoud sets the Gospel of Mark as quite distinct from the Basilides is said to have written. Mark was addressing those persecuted at the time of Bar Kochba and his Little Apocalypse refers to the deeds of Hadrian and Bar Kochba. (Compare Herman Detering’s more recent argument for this.) Matthew, said to represent more Jewish Christians, wrote a more acceptable revision of this. Then John, and finally Luke.
And that is Paul Louis Couchoud‘s basic idea of how the gospel narratives got going.