First, virtually all scholars acknowledge that the gospels are not written in the literary genre of mythology or folklore or allegory. They are written in the genre of historical writing, specifically in the genre of ancient biography (I recently mentioned this here as well). The significance of this is that the understanding of how these different genres functioned in ancient literature only became known in the Modern era. Thus, in order to maintain the myth hypothesis, one would have to argue that the NT authors anticipated Modern discoveries and categories of thought, and then intentionally wrote a myth as if it were a biography in order to trick future analysis of their writings. This is obviously absurd.
Second, in order to find these parallels, the categories have to be so broad that they can apply to virtually anything. "Death and rebirth" (or alternately, "resurrection") means any kind of change, since you’re "dying" to the old way and being "reborn" to the new. To take another example, I’ve read a few dozen myths, or accounts of myths, that contain the "virgin birth" motif. So far, I can group them into three categories:
1) Virgin births in which the woman becomes pregnant by having sexual intercourse with a hero or god.
2) Virgin births in which the woman becomes pregnant via a substitute form of sexual penetration (the hero or god leaves his "seed" in a pool, a woman bathes in the pool ...).
3) Virgin births in which it is not related how the woman became pregnant.
It’s just weird to refer to a birth initiated by a woman having sex as a "virgin birth". And obviously, none of these categories parallels the virginal conception of Jesus, in which no sexual penetration of any kind took place. The only way these are similar to Jesus is that a woman became pregnant, and the supernatural is somehow involved. Thus we see that the people who call these myths "virgin births" are using Christian terminology so that the parallels don’t appear as vague -- then they turn around and marvel at the similarities.
Third, the attempt to compare Jesus to mythologies is completely rejected by historical Jesus scholarship, and has been for nearly a century. It still lives on in popular culture and college campuses, no doubt partially because many teachers and professors of other fields are unaware of historical Jesus scholarship, and use the classroom as a platform to expound their (mis)understandings of the nature of Christianity. Even C. S. Lewis thought that there were many parallels to Jesus in world mythology, but ironically, it actually played a role in his conversion to Christianity -- the parallels were there to "prepare the way" for acceptance of Jesus. In Christ, "myth became fact". Nevertheless, historical Jesus scholars believe (very reasonably) that Jesus should be understood in the context of first century Judaism rather than myths that have little to no similarities to Jesus, and at any rate had no historical connection to him and the early Church.
This leads me to my final point (in this post and this series): modern scholarship. When I first turned to historical Jesus studies to try to find a way to reject traditional Christianity, I was shocked at how much they accept. But others coming from a different direction may be equally shocked at how much they deny. I think a good case can be made based solely on what the scholars acknowledge as historically demonstrable, but here I’d like to focus on the perils of scholarship.
C. S. Lewis wrote a very succinct essay called "Modern Theology and Biblical Criticism" (alternately titled "Fern-seed and Elephants" for reasons you’ll soon discover) in which he delineates a few of the problems with modern attempts to reconstruct a portrait of Jesus different from what the NT relays. While volumes of books have done this extensively, Lewis’s treatment deserves a detailed exposition.
First, bearing in mind that Lewis was a literary expert, he claims that many of these critics demonstrate a lack of literary judgment. After giving several examples of this he concludes, "These men ask me to believe they can read between the lines of the old texts; the evidence [against this] is their obvious inability to read (in any sense worth discussing) the lines themselves. They claim to see fern-seed and can’t see an elephant ten yards away in broad daylight."
Second, Lewis points out that these critics claim that Jesus’ followers were completely wrong about who he was and what he did, but that they’ve recovered this information by reading the records his followers left behind. Lewis gives a few other examples of this sort of reasoning:
One was brought up to believe that the real meaning of Plato had been misunderstood by Aristotle and wildly travestied by the neo-Platonists, only to be recovered by the moderns. When recovered, it turned out (most fortunately) that Plato had really all along been an English Hegelian rather like T. H. Green. I have met it a third time in my own professional studies; every week a clever undergraduate, every quarter a dull American don, discovers for the first time what some Shakespearean play really meant. But in this third instance I am a privileged person. The revolution in thought and sentiment which has occurred in my own lifetime is so great that I belong, mentally, to Shakespeare’s world far more than to that of these recent interpreters. I see -- I feel it in my bones -- I know beyond argument -- that most of their interpretations are merely impossible; they involve a way of looking at things which was not known in 1914, much less in the Jacobean period. This daily confirms my suspicion of the same approach to Plato or the New Testament. The idea that any man or writer should be opaque to those who lived in the same culture, spoke the same language, shared the same habitual imagery and unconscious assumptions, and yet be transparent to those who have none of these advantages, is in my opinion preposterous. There is an a priori improbability in it which almost no argument and no evidence could counterbalance. (emphasis mine)
Third, as discussed in parts 1 and 2, these scholars equate "miraculous" with "unhistorical". This is simply a philosophical bias which can be (and has been) refuted. When a historian bases his theories on bad philosophy instead of historical evidence, he has ceased to speak to us as a historian.
Lewis’s fourth, and best argument is as follows:
What forearms me against all these Reconstructions is the fact that I have seen it all from the other end of the stick. I have watched reviewers reconstructing the genesis of my own books in just this way. ... I have watched with some care similar imaginary histories both of my own books and of books by friends whose real history I knew. ... Now I must first record my impression; then, distinct from it, what I can say with certainty. My impression is that in the whole of my experience not one of these guesses has on any one point been right; that the method shows a record of 100 percent failure. You would expect that by mere chance they would hit as often as they miss. But it is my impression that they do no such thing. I can’t remember a single hit. But as I have not kept a careful record my mere impression may be mistaken. What I think I can say with certainty is that they are usually wrong. ... Now this surely ought to give us pause. ... In order to decide how reliable the method is, what more could you ask for than to be shown an instance where the same method is at work and we have facts to check it by? Well, that is what I have done. And we find, that when this check is available, the results are either always, or else nearly always, wrong.
We can contrast this with the second point to make this even clearer: if those that lived in the same culture, spoke the same language, and shared the same habitual imagery and unconscious assumptions as Lewis could not reconstruct an accurate history of any of his works, how likely is it that those doing this with the gospels, who are working without these advantages, would do so successfully?
I don’t mean to imply that scholarship is a crock; far from it. Just that when it comes to the NT, some people hold it to different standards than they do other ancient documents. When held to the same standard, NT history is established at least as firmly as classical Rome and Greece. If it wasn’t for a bias against what the NT documents record, no historian in the world would ever doubt them. As Kreeft and Tacelli write,
If the books of the New Testament did not contain accounts of miracles or make radical, uncomfortable claims on our lives, they would be accepted by every scholar in the world. In other words, it is not objective, neutral science but subjective prejudice or ideology that fuels skeptical Scripture scholarship.
(see also part 1, part 2, part 3, and part 4)