If you go to see Mel Gibson’s film, “The Passion of the Christ,” there are a few things you should know. I’m not referring to the gratuitous violence and endless gore, served up (in true Hollywood style) in agonizing slow-motion sequences. Much has already been made of this in the media, and there is no need to dwell on it further.

No, I’m talking about the fact that this movie, which tries in many ways to tell the story of Jesus’ death “as it was,” is largely a work of fiction. It departs widely from the Gospel accounts of Jesus’ Passion; it departs even further from what is likely to have happened historically.

There is an inherent difficulty in depicting the final hours of Jesus’ life (and, indeed, much of his earlier life) on the basis of the four Gospels. The Gospels tell a similar story, but the accounts do not agree on significant details, such as the day of Jesus’ death (on the Passover or after it?) or his dying words (three different versions in four gospels). There are also scenes at which no reporter was present (conversations between Jesus and the Roman procurator Pilate).

Gibson circumvents this problem by picking and choosing different material from different Gospels. In the case of Jesus’ dying words, Gibson includes all three versions. As a result, the film is not faithful to any single Gospel but is a strange amalgam based on who-knows-what criteria. When an event occurs in only one Gospel, Gibson usually includes it, e.g., the sending of Jesus to Herod (only in Luke 23:6-12) or the “conversion” of one of the criminals crucified with Jesus (only in Luke 23:40-43). An exception is when the story is odd or embarrassing, e.g., the curious incident of the young man in the linen garment who is seized with Jesus and then runs away naked (only in Mark 14:51-52). Gibson discretely omits this.

As for the dialogue and much of the teaching of Jesus (shown in the film’s flashbacks), Gibson prefers material taken from the Gospel of John, although this is the Gospel that differs most from the other three and that has the least likely claim to historical reliability.

At times, Gibson exaggerates tendencies found in the four Gospels. On the controversial question of the role of certain Jewish priests in the arrest and condemnation of Jesus, Gibson follows the Gospels in exonerating Pilate and blaming the high priest Caiaphas. But Gibson goes beyond the Gospels (and beyond history) by portraying the Roman procurator as a sympathetic figure who is virtually coerced by the Jewish leader into crucifying Jesus. Gibson even creates a scene in which Pilate’s wife consoles Mary, the mother of Jesus, and gives her a cloth to mop up Jesus’ blood. This is neither biblical nor historical.

Gibson’s constant insertion of fantastic, non-biblical material into the story is one of the most distracting — and, occasionally disturbing — features of the film. Those familiar with the story of Jesus’ arrest on the Mount of Olives will be surprised to see Gibson has created a temptation scene, complete with a demonic figure with a maggot in his/her nose and a tail that turns into a serpent! This demonic character appears frequently throughout the film, apparently as a cipher for Gibson’s own theology of the Passion as a struggle between pure good and pure evil.

Many other examples of extra-biblical intrusions could be cited. Almost all of the scenes involving Mary are derived from later Christian legend and not the gospel stories. Such additions reflect Gibson’s own traditionalist Catholic piety. Catholics familiar with the Stations of the Cross will recognize that Gibson’s presentation owes as much to this late medieval practice as to the biblical accounts of Jesus’ Passion.

Gibson’s film has been likened to a classical “Passion Play,” a genre with its own ambiguous history. I think it is closer to an “apocryphal” gospel. In the early centuries, Christians produced numerous imaginative retellings of the Gospel stories, often with the same kind of fantastic elements recreated by Gibson.

Such stories nourished Christian piety, as Gibson’s story is certain to do; they often fostered heresy as well. If you see Gibson’s film as a Christian believer seeking inspiration, you may not be disappointed. Just don’t confuse his story with the Bible or history.

David Hunter is a professor of religious studies and holds the Monsignor James A. Supple Chair of Catholic Studies. He viewed “The Passion of the Christ” Tuesday at a screening in Urbandale.