The first chapter, by Robert Price, presents the "mythicist" view: that Jesus was not a real, historical person, but was from the beginning a fictional character in an invented myth. While this is a popular view among some atheists, it is a view held by hardly any actual New Testament scholars. (I have attempted to summarize the main arguments elsewhere.)
McGrath nicely exposes the difficulties in Price's approach:
And this is where we can return to Price's ignoring of his own stated principles. He states that everything is possible in theory, and so asks what is probable. And yet he never shows that the scenario he envisages for the emergence of Christianity and its narrative texts is anything other than possible, at best, and that provided one is willing to assume a number of controversial points which likewise remain unjustified.
For instance, is it possible that early Christians went through the Jewish Scriptures, choosing a story here, a turn of phrase there, and weaved them together to create a fictional Messiah? Certainly - as are all other scenarios. What is never explained is why someone would have done this, much less done it to produce a crucified Messiah rejected by his contemporaries. If nothing else, Price's mention of Occam's Razor at this juncture seems so ironic as to be comical (p.74). How is an unparalleled process of fabricating a fictional Messiah from texts that would have had to have been painstakingly combined a simpler explanation than that there was a historical figure of Jesus, about whom stories were sometimes created to fill in gaps in his followers' knowledge or to cause him to address issues that he had not?
Price has shown that it is indeed possible to imagine a scenario in which Jesus was invented - that was never in dispute. But his chapter has also demonstrated, I believe, that historians are right to favor the conclusion that Jesus existed, however obscured by legend he may be from our view. Because if we consider the weak and tendentious case Price made for his conclusions, having emphasized that it is not possibility but probability that he needs to demonstrate, then I can only conclude that it is the best case that can be made for mythicism, since there is no one that I know of who is trying to make a case for mythicism that has better and more relevant qualifications than Price does.
I'm not entirely in agreement with that "best case" bit: Earl Doherty, though not having the qualifications that Price has, has developed a more detailed mythicist scenario. But I'm glad to see NT scholars engaging the mythicist position and explaining their reasons for rejecting it. This chapter, and the responses to Price from the other contributors, looks to be an important contribution to public understanding of the issue.