Amid the million sensational novels which I have devoured with the most agreeable sensations, I remember one [* see postscript] which was really very thrilling; and the thrill consisted in the well concealed and well betrayed secret that there still exists in the world a group continuing the ancient and mysterious rite of Nemi; the temple of Diana where the priest sacrificed the priest. The story was so well told that the reader did really feel something like the icy shock of antiquity. He realized something unnaturally moving in the mere fact that a religion had somehow managed to survive out of ancient Roman times. Few of those who read that novel would pause to reflect that a religion really has survived out of ancient Roman times. But nobody notices it, because it is not secret but public; because it is not cruel but humane; and because in that antique Italian idolatry, it is not the priest but the god that died. [cf. my Easter quote from The Everlasting Man CW2:295-6]
Nevertheless, it is only by some such angle almost of accident, that it is possible to put a finger in that nerve of fear and unfamiliarity, by which we can really accept the stupendous fact that has happened. In one sense the idiots are perfectly right when they say that the Christian religion is but a continuation of the Pagan religions. Only it was nothing in the Pagan religions themselves that could possibly continue. It was in itself a Christian miracle to make Paganism live. When we look at the Mass, we see something that the heathens saw; the only thing that remains of them or their seeing. Despite the delights of the detective narrative I have mentioned, we most of us knew very well that there is not a modern priest of Diana quietly cutting the throat of the late incumbent of his parish. But there is something pretty nearly as old and every bit as sensational. The story is not only a romance, it is in the first derivative sense a novel; in that it is still novel, or has not left off being news.
The first example of this is that the very garments of the priests standing at the altar are essentially the garments of a man of ancient Rome, or even of heathen Rome. In being handed down for hundreds and hundreds of years, they have of course been modified in pattern, but they preserve the ancient plan. What looks so strange to us in a man standing at the altar would hardly have looked so strange to Horace or Catullus in a man walking in the street.
[GKC The Resurrection of Rome CW21:455-6]
...it was a very special idea of St. Thomas that Man is to be studied in his whole manhood; that a man is not a man without his body, just as he is not a man without his soul. A corpse is not a man; but also a ghost is not a man. The earlier school of Augustine and even of Anselm had rather neglected this, treating the soul as the only necessary treasure, wrapped for a time in a negligible napkin. Even here they were less orthodox in being more spiritual. They sometimes hovered on the edge of those Eastern deserts that stretch away to the land of transmigration; where the essential soul may pass through a hundred unessential bodies; reincarnated even in the bodies of beasts or birds. St. Thomas stood up stoutly for the fact that a man's body is his body as his mind is his mind; and that he can only be a balance and union of the two. Now this is in some ways a naturalistic notion, very near to the modern respect for material things; a praise of the body that might be sung by Walt Whitman or justified by D. H. Lawrence: a thing that might be called Humanism or even claimed by Modernism. In fact, it may be Materialism; but it is the flat contrary of Modernism. It is bound up, in the modern view, with the most monstrous, the most material, and therefore the most miraculous of miracles. It is specially connected with the most startling sort of dogma, which the Modernist can least accept; the Resurrection of the Body.
[GKC St. Thomas Aquinas CW2:433-4]
* Postscript: I am still trying to locate this novel. Going only from the title, one possibility is The Crime of Diana's Pool, by V. L. Whitechurch, which appeared in 1927 and so is a possibility; however I have not yet located that book to see if the story fits. If you have read it, or if you have any alternative suggestions as to what book GKC is referring, please let me know.