Like most such books, this is based on the unsupported assumption that there was a "Jesus" as depicted in the Gospels, i.e. that the Gospels and Acts are history. They are not. Let me give here a few bits from the introduction of my not-yet-published book (but soon!) on the topic of Jesus:
Classical historian Richard Carrier has done an amazing job collecting the best evidence and arguments in his 2014 book
On the Historicity of Jesus: Why We Might Have Reason for Doubt, following in the footsteps of such names as Michael Goulder, G. A. Wells, Gerd Ludemann, Robert Price, Earl Doherty, and Thomas Brodie.
Carrier limits the scope of what he intends to prove, but the breadth of evidence he examines is admirable. His main task is to determine which is more likely: a “minimal” argument for so-called mythicism, or the same for historicity. In other words, was there an actual man named Jesus who acquired followers, was claimed to have been executed by Jewish or Roman authorities, and who came to be worshiped as a god soon after? Or was Jesus originally conceived as a celestial deity who communicated via divine inspiration, faced an ordeal of death and resurrection in heaven, whose story was then written in allegorical form, which later worshipers took to be a real account of his time on earth?
Carrier analyzes the question from all angles: the early Judeo-Hellenistic background, the precedents for each type of figure (mythicized humans and historicized gods), the biblical and non-biblical evidence, including Acts, the Gospels, and the Epistles. His conclusion is inescapable: the mythicist position is simply more likely. Not only do the earliest sources support the “celestial deity” option, the rest of the evidence does not support the historical one. The authors of this work are convinced. . Any history of Christian origins should start on the basis of the minimal mythicist position.
For the earliest Christians like Paul, “Lord Jesus Christ” was a mythical/supernatural being though we intend to propose that Paul was inspired by a real historical person and events. Further, while one or more additional historical individuals may have provided the writers of the Gospels with material for their depictions of Jesus, the figure(s) they ended up creating are entirely literary creations. This is a standard practice: mythical creations incorporate stories and elements from various cultures and eras, and real and fictional characters, all unified in a new form. King Arthur is a perfect example.[3] Others include Ned Ludd, the mythical founder of the Luddite movement who later had letters forged in his name, even complete biographical novels, despite there being zero evidence for his existence. Or “Tom Navy” and “John Frum” of Melanesian cargo cult fame. Even Moses and Daniel, from the Old Testament.
This is like the way modern novelists may include aspects of their friends or famous personalities in their characters, who are otherwise entirely fictional. For example, Harry Potter does not exist, but aspects of his character may be inspired by real people of J.K. Rowling’s acquaintance. Additional characters from real life may be added for verisimilitude – for example, setting a fictional story about a fictional character in a time period where real people appear, e.g., when the
X-Files made reference to Bill Clinton, Janet Reno, or George W. Bush.
The Apostle Paul is arguably the most important figure of early Christianity. The writings attributed to him make up about one third of the New Testament, making him the most prolific author of the early Church. The book of Acts features him as a main character, along with Peter and, aside from a few other short books in the NT that were perhaps written in the same time period (Hebrews, James, 1 Peter, Jude, parts of Revelation), he is widely regarded as the
earliest Christian writer.
These trends indicate what a tiny minority have been saying for years: that the search for a historical Jesus of Nazareth, as depicted in the Gospels, only leads to negative returns. So naturally, the focus has turned to Paul, the earliest Christian author.
The study of Paul has taken on an all-new importance in recent years due to the development of new critical methods. The latest and best research utilizing those methods suggests a number of things. First, the Gospel accounts of Jesus’ life, preaching, death, and resurrection are relatively late writings; mainstream researchers place them anywhere from 40 to 100 years
after the events they claim to narrate (with a growing minority favoring dates closer to 100 years after, in the early to mid second century). Second, more researchers are recognizing that the Gospels are primarily literary in nature. They are more akin to historical novels and myths than real history.
Acts presents itself as a history of Christianity after Jesus, following the careers of Peter and Paul, Christianity’s two most famous apostles. As Richard Pervo has made abundantly clear in his detailed studies, it is no such thing. Rather, it is another second-century “historical novel” with an agenda, just like the Gospels. (Which makes sense, as its author was in all likelihood the same as the author or redactor of the canonical Gospel of Luke.)
To put it simply, the author of Acts picked out some authentic names and events from texts extant in his time and wrote his novel around them, with the purpose of presenting the image that everyone got along in the early church. They didn’t, as we’ll see. Paul’s letters paint a very different and contradictory picture. In methodological terms, Acts is not a historical document, but the letters of Paul
are.
What documents might the author of Acts have used to create a plausible setting for his narrative? And to which contemporary sources can we turn for the historical context we need in order to place Paul’s life and work? The only historian whose works have survived to give us a detailed picture of the times and places in which Paul lived and worked is Joseph bar Matthias AKA Titus Flavius Josephus, who lived ca. 37–100 AD. This places his work about one generation after Paul, who is said to have been active in the late 30s through to the 50s or 60s AD. As Pervo argues, the author of Acts likely used Josephus’ works; they weren’t simply drawing on the same historical sources.
However, we encounter a similar problem with Josephus that we encounter with the Gospels and Acts: even though Josephus claims to be writing history, we cannot necessarily rely on using his works as accurate historical sources. As modern Josephus scholars point out, researchers must be careful before accepting what he wrote at face value. And this means we must also account for this when analyzing how
ancient authors used his works, like the authors of the Gospels and Acts. They too could not have known that much of what Josephus wrote was embellished or falsified.
Later Christian writings cannot be relied upon for real history. And even the contemporary sources with the most relevant context are of often-dubious reliability. So we are surrounded by problems. Paul’s letters are arguably the earliest Christian historical documents, the only firsthand source we have for many events and ideas. So it should go without saying that we need to utilize them conscientiously and effectively. But even reading
them with the genuine history of the time firmly in mind can be problematical, as the work of Baur, Knox, Lüdemann, Trobisch, Price, Tyson, BeDuhn, Campbell, and others reveal. In general, we have to keep in mind that conflicts between pagans and Christians often led to wars of words, particularly the written word. Additionally, the history of the destruction and redaction of texts is appalling.