"Any close scrutiny of his life must take account of the importance of his religion. His commitment to Christianity and, in particular, the Catholic Church was total."
-Humphrey Carpenter J.R.R Tolkien a Biography Houghton Mifflin Company Boston New York 2000

"The Lord of the rings and, by extension, his broader legendarium, is at its core and foundation, or as one might say in its essential nature, based on religious, and specifically Catholic, beliefs and thought."

-Carl F. Hostetter The Nature of Middle-earth Late Writings on the Lands, Inhabitants, and metaphysics of Middle-earth Houghton Mifflin Harcourt Boston NY 2021

"Tolkien Christian faith-inspired and informed the writer's imagination...transcendent truths of Christianity bubble up throughout this story."
-Kurt Bruner and Jim Ware Finding God in the Lord of the Rings Salt River 2001


In letters 142, Tolkien wrote "The Lord of the Rings is, of course, a fundamentally religious and Catholic work," And "I am a Christian and of course what I write will be from that essential viewpoint." In letters 233, he said the morality of his work "is explicitly linked to the Lord's Prayer." His writings were in no way an allegory for Christianity; instead, Tolkien said, "the religious element is absorbed into the story and the symbolism." Carpenter said, "he wanted the mythology and legendary stories to express his own moral view of the universe." As such, he included many Christian themes in his works and as a devout Catholic, Tolkien's worldview could not be hidden from his works.  

His faith influenced his writings to such a degree that he expected to be known as a Christian author by any who read his mythology, "I am a Christian, that fact can be deduced from my stories." David Day in The Battles of Tolkien quotes Tolkien as saying, "myth and fairy-story must, as in all art, reflect and contain in solution elements of moral and religious truth." At a lecture at Saint Andrew's, Tolkien said it was specifically a Christian venture to write The Lord of the Rings. And at the presupposition level, his mythology is Christian. W.H Auden observed: "the unstated presuppositions of the whole work are Christian." Author, Devin Brown in The Christian World of the Hobbit, writes, "Tolkien's Christian beliefs are a fundamental part of the story from start to finish." 

His writings were not, nor were they intended to be a Gospel tract. Yet, The Lord of the Rings has even converted some to Christianity. A recent politician running for governor in my home state of Vermont was converted in part due to Tolkien. Another example is an online account by Fredric Heidemann, I was an atheist until I read Lord of the Rings. Finally, I know of an online acquaintance who was converted simply by reading The Lord of the Rings. An atheist wrote Tolkien, "you create a world in which some sort of faith seems to be everywhere without a visible source, like a light from an invisible lamp." This was the kind of effect Tolkien desired. 

To the devout Catholic Tolkien, the modern world had fallen from the faith. So he tried to convey his faith through a tale in a way that might be more acceptable and better received. God himself is known as a storyteller as he uses that method often in the Bible. In The Secrets of Middle-earth, Carpenter says, "It is a very religious book... it's a book that tries to convey the feeling of religion to a world which is not actually a believing world...a godless modern world." 

Tolkien never saw himself as the actual author of his works since, without God, he would have no mind, and since his imagination originated from God, his stories did as well. Because of this understanding, Tolkien also believed that "the only just literary critic is Christ," because of "the gifts he himself bestowed." How true he was to Christ in his writings mattered more than any human critic. His fantasy had only entered his mind because God had first created his imagination, so, in a way, he just discovered what had originated from God. Or, as Carpenter described, "his imaginative inventions must originate from God, and must, in consequence, reflect something of eternal truth." Tolkien said he felt a spirit was working through him while writing, which he attributed to God.

Please elaborate

I was just mocking his attitude that fiction can be heretical. By his logic, the nursery rhyme Baa Baa Black Sheep is also heretical for the reasons I gave. Keep it away from your kids!!!

But Milton’s “Paradise Lost” was also fiction, and ended up on the Index presumably because it contained heresy (granted, Milton was discussing an historical event connected to revelation, whereas Tolkein’s work is completely unrelated).

Well for one it was severely blasphemous, and the other is to what extent it was intended to be fictional is questionable. Milton is known to have had strange and heterodox beliefs even by Protestant standards.

It's not really on the same level as a fairy tale. I mean many of the myths and fairy tales of the past are only available to us because Catholic monks transcribed them. They actually went out of their way to preserve these stories.