C.S. Lewis, J.R.R. Toklien, and...George MacDonald?

WorldNetDaily has published a very good article about Christianity and fantasy/sci-fi:

The Christian foundation of the other famous Inkling's work is less blatant, yet almost as obvious to all but the most willfully blind. While there have been a few brave souls foolhardy enough to attempt to deny the self-evident, even those with no discernible Christian agenda freely acknowledge the powerful religious elements integral to 'The Lord of the Rings.' For the Secret Fire of which Gandalf is a servant, as Tolkien explained for the benefit of those too unfamiliar of the book of Acts to recognize the symbolism, is nothing less than the Holy Spirit whose flames were first seen at Pentecost, and in case things were not perfectly clear, the author once described his landmark trilogy as 'a fundamentally religious and Catholic work.'

Thus, it is not the fantasy elements--which are actually not very similar in the particulars--but the Christian themes running through both that tie Lewis' and Tolkien's works together in our minds. Nor are these themes the only relationship. Tolkien, Lewis and Williams were all influenced to varying degrees by the same literary and spiritual mentor, a Scottish minister and prolific author by the name of George MacDonald. MacDonald is largely forgotten now, but he was a well-known author of the late 19th century--among other things, he corresponded regularly with a certain American writer he had befriended by the name of Samuel Clemens. In one letter, Clemens even mentioned to MacDonald how his daughter Susy had worn out her copy of MacDonald's 'At the Back of the North Wind' and requested that MacDonald send her a replacement.

I have to admit, I've never heard of MacDonald. Looks like I have some reading to do.