<P> Mark, for example, is not biography in the modern sense but an apocalyptic history depicting Jesus caught up in events at the end of time . </P> <P> As Luke's attempt to link the birth of Jesus to the census of Quirinius demonstrates, there is no guarantee that the gospels are historically accurate . The gospel authors altered the traditions at their disposal (their sources) to serve their own ends--thus Matthew and Luke have frequently edited Mark, and the contradictions and discrepancies between John and the synoptics make it impossible to accept both as reliable </P> <P> A second problem is that the gospels as we have them are not the originals, but have been edited and recopied over time, and evidently differ from them in thousands of ways . In that long chain of transmission the texts have been corrupted, leading Origen to complain in the 3rd century that "the differences among manuscripts have become great,...(because copyists) either neglect to check over what they have transcribed, or, in the process of checking, they make additions or deletions as they please ." </P> <P> Despite all this, scholars are confident that the gospels do provide a good idea of the public career of Jesus, and that critical study can attempt to distinguish the ideas of Jesus from those of later authors and editors . </P>

When were the gospels written and by whom