In the nineteenth and twentieth centuries, the History of Religions/Comparative Religion/Comparative Mythology schools were often taken to have discredited the Christian faith by showing similarities between Christian narratives (such as that of the life, death, and resurrection of Jesus) and various pagan mythologies—most famous here perhaps is the treatment of the dying and rising god by James Frazer and the Cambridge Ritualists. If such tales are common and widespread, there is nothing unique about Christianity; the Christians may have borrowed such stories from the surrounding culture, or they may answer to something deep the human psyche, but in any case there is nothing supernatural or objectively redemptive about them. Christian beliefs are thus relativized by comparison with other similar beliefs, and this process brings with it the necessary corollary of agnostic religious pluralism.
What is, I think, most interesting about this line of argument is that it is actually a Christian line of argument, or rather the inversion of a Christian line of argument, that first appears (to my knowledge) in the First Apology of Justin Martyr, 1 written around 155 in the reign of Antoninus Pius.
Justin does not deny similarities between pagan myths and the Christian Scriptures (especially, in the First Apology, with reference to the Hebrew Scriptures): he fully embraces them, but argues that the originary source of such tales is the Bible, perversely imitated under demonic influence and guidance by the creators of pagan mythology, such that the resemblance of Christian stories and their pagan counterparts actually becomes an argument for the truth of the Christian faith rather than its falsehood:
But those who hand on myths invented by the poets offer no demonstration to the youngsters who learn them–indeed I [am prepared to] show that they were told at the instigation of wicked demons to deceive and lead astray the human race. For when they heard it predicted through the prophets that Christ was to come, and that impious men would be punished by fire, they put forward a number of so-called sons of Zeus, thinking that they could thus make men suppose that what was said about Christ was a mere tale of wonders like the stories told by the poets. These stories were spread among the Greeks and all the Gentiles, where, as they heard the prophets proclaiming, Christ would especially be believed in. But, as I will make clear, though they heard the words of the prophets they did not understand them accurately, but made mistakes in imitating what was told about our Christ. (First Apology 54)
If Justin is right, of course, then such modern approaches have been coopted by demons and these schools are themselves are guilty of what they claim the Christians are guilty of!
More broadly, one can say, first, that often the categories used to criticize the Christian faith in the history of Western scholarship are parasitic on that same faith; without their host, such schools would have very little to say. The comparative approach is very old, and it was first deployed by Christian apologists.
Second, the fact of similarities between Christian Scripture and other mythologies doesn’t prove anything in and of itself. There are various ways in which it can be glossed as testimony to the truth. Justin’s is one; Tolkien in “On Fairy Stories” is another:
But in God’s kingdom the presence of the greatest does not depress the small. Redeemed Man is still man. Story, fantasy, still go on, and should go on. The Evangelium has not abrogated legends; it has hallowed them, especially the ‘happy’ ending’. The Christian has still to work, with mind as well as body, to suffer, hope, and die; but he may now perceive that his bents and faculties have a purpose, which can be redeemed. So great is the bounty with which he has been treated that he may now, perhaps, fairly dare to guess that in Fantasy he may actually assist in the effoliation and multiple enrichment of creation. All tales may come true; and yet, at the last, redeemed, they may be as like and as unlike the forms that we give them as Man, finally redeemed, will be like and unlike the fallen that we know.
As Hamlet says, “There are more things in heaven and earth, Horatio,/Than are dreamt of in your philosophy.” Hamlet’s words prove wise when confronted with the academic and intellectual tendency to naturalize the history of the Spirit.