1) Can a Christian Author be indebted to an Anti-Christian one? , 2) What does Subcreator Mean?
It is possible that José Antonio Primo de Rivera was in some way indebted to Marx. Once he called him "a talented Jew, who saw the problem with Capitalism, but not the solution to Capitalism."
St Paulinus of Nola was mentored by Ausonius, who was not just Pagan, but even homosexual.
And, of course, C. S. Lewis had some debts in literary and mental make up to Anti-Christians.
Edith Nesbit was both Fabian Society and, possibly (on a list of known or alleged members!) Golden Dawn. This did of course not bother C. S. Lewis in his childhood, he was just happy to read her books.
James George Frazer in The Golden Bough was in a Darwinian fashion tracing the thought of mankind in the stages magic, religion and science, much as the Positivist Comte traced it in mythology, metaphysics and positive science. Obviously he was Anti-Christian. And as obviously C. S. Lewis enjoyed him while he was an Atheist.
William Morris, who was a great author of fantasy and a great exponent of Medievalism was also a revolutionary socialist. Hardly a strict if at all Christian. He was enjoyed by both C. S. Lewis and J. R. R. Tolkien.
So, if C. S. Lewis was reading these before becoming a Christian, was it his duty to renounce them at conversion? In all of their works, in all of their thoughts, in all of their novels and nostalgia for Middle Ages as well as for Paganism?
Morris is not on the Index. Nesbit is not on the Index. Even Frazer is not on the index. If it had been either C. S. Lewis' duty when converting to Christianity or Tolkien's when taking his Catholicism seriously, to renounce these authors, the Church should have said so.
Is there a reason why these are not on the index?
Let's start with Frazer. The details of paganism are the main content of his work. His ideology - which is indeed antichristian - is absent from its pages, meant to be gathered between the lines, perhaps alluded to in a foreword, but it does not determine any content to be included which is factually erroneous. And facts about Paganism are not Anti-Christian errors. Even if presented by one Anti-Christian.
Then Morris may have hated Capitalism in a somewhat wrong way, if he thought Marxist Socialism a solution. But it is a wrong thing and Medieval Guilds were partly there to prevent it. As for the rest, the Middle Ages, which he did not quite admire in all respects in the right way, were admireable, since they were the product of Christianity. Which Chesterton (notably in Return of Don Quijote) and Tolkien fully appreciated, even if Morris did not. However, he did realise the falling away from them, Industrial Capitalism, was a product of esp. Calvinist Protestantism, which he duly found unattractive.
Of course, if he once said "love is enough", he was, if speaking of human loves, wrong. He needed to be contradicted. He was - by his admirer C. S. Lewis. The intro to his The Four Loves, or the post script, whichever, says the novel so entitled (actually the title was somewhat longer: Love is Enough, or The Freeing of Pharamond: A Morality, 1872) got its briefest review in the few words "it isn't" - and the book by CSL agreed largely with that assessment. Only adding that preventing human loves is not the recipe for curing their mistakes.
Note, this book (by CSL, I haven't read the one by Morris) is not limiting the mistakes to those of Eros, his third love. There is a kind of paternal or parental possessiveness which is about Affection, his first love. There are kinds of intellectual pride, which are about Friendship, his second love. And Eros can be hallowed in marriage, while the other two loves here mentioned are not usually so.
And Nesbit ... like Morris, also Nesbit wrote for the large public. They adapted to its tastes, which were very much more Christian than when Rowling wrote Harry Potter. Also, like Morris, Nesbit did have sensible things to say, about cooperation among siblings or about preference for less competitive and more wellproductive but not overproductive economies, like pre-Industrial Revolution.
Nevertheless, some errors were expressed but on the other hand their readers C. S. Lewis and J. R. R. Tolkien actively strove to take the good and avoid or correct the bad from Nesbit (CSL) or Morris (CSL & JRRT). If one has read an author with delight who does express some bad things, either avoiding the author or this method of sifting and correcting are the correct ones, when you realise this fact.
And this was, by temperament, the path they chose, but also because the authors in question were not so heavily and overtly anti-Christian in their writings as to have merited for instance inclusion on the index of forbidden books. Which is a thing Tolkien would have known and a thing which was sufficiently apparent from the texts for C. S. Lewis to sense it even if he did not know this fact about the Index.
So, yes, despite being indebted to Anti-Christian authors, they are themselves Christian authors. Not flawless, but not so bad as to merit the comparison I have heard over the web or orally here, namely with the Apocrypha on which St Jerome had a few things to say in the previously quoted letter:
Let her avoid all apocryphal writings, and if she is led to read such not by the truth of the doctrines which they contain but out of respect for the miracles contained in them; let her understand that they are not really written by those to whom they are ascribed, that many faulty elements have been introduced into them, and that it requires infinite discretion to look for gold in the midst of dirt.
C. S. Lewis and J. R. R. Tolkien saw to it that their readers did not have to use infinite discretion, simply by using what discretion they had themselves. This was especially so in Tolkien, who was a Catholic.
This is why I think a Christian need not blush to read them.
As for the charge that they were secretly Illuminati, I think it is totally erroneous. It was made by John Todd while CSL had already been dead and JRRT was close to death, therefore neither had an opportunity to respond. Also, it may be informative if one author is very erroneous anyway - like Marx and Engels are - to know he was secretly of such and such an occultist obedience or even a diabolist (see further Wurmbrandt's study Was Karl Marx a Satanist? which he concludes in the affirmative), but supposing someone were so does not prove his writings to be erroneous.*
Other charges have come by supposing it was CSL's fault if Narnia Chronicles are required reading for Wiccans (in fact, CSL is very anti-witchcraft), or by playing on double meanings of the word "magic" where CSL and JRRT use the word loosely, as in any supernatural facts or acts, whereas critics use it about the mortal sin by which human beings seek to procure such powers by an implicit or explicit contract with demons. This thing was of course not anything these authors recommended, indeed a thing they warned very heavily against (confer Angmar's obtaining certain powers by a ring given by Sauron - essentially Abaddon - to mortals, and the horrible effect this has on his being and will, when it comes to Tolkien).
So, whether the authors CSL and JRRT were indebted to were anti-Christian or merely un-Christian, in the cases here mentioned and very well known, they were themselves Christians.
As to Yeats, CSL confesses his earlier infatuation with him as a sin and a weakness, and his writing of certain warnings can be seen as a kind of penance for it.
Hans Georg Lundahl
St Ursula and 11 thousand Virgins
* Writers are not politicians. If one such is a quockerwodger (explanation, see this link: here, English Historical Fiction Authors : Old Words – London Street Slang from the 1600s to the 1800s, don't vote for him, or he'll betray you. These writers are already dead and can no longer give the general readership any bad surprise. Perhaps it is not surprising that the charge should be made in France where, as Fr. Bryan Houghton said, everything turns on politics. French, even if Catholics, apply the categories of politics to things like ... well, authors.