Middle-earth
Another example is C. S. Lewis's "Space Trilogy," in which Earth is also called Middle-earth. Lewis's novels are situated at the approximate time of World War II, with the last novel, "That Hideous Strength," taking place in post-war England, and they specifically bring in references to Tolkien's legendarium (at that time largely unpublished) and treats these references as primary fact within Lewis's fiction. Merlin, of King Arthur fame, is treated as a successor to the Atlantis magic found within "Numinor" (Lewis's unintentional misspelling of Númenor), and similarities can also be found in the Quenya name for Númenor, which is "Atalantë," and Lewis specifically references the earth as Middle-earth twice, both in Chapter 13, "They Have Pulled Down Deep Heaven on Their Heads". Lewis's borrowings came directly from Tolkien himself: they were close friends and shared each other's literary creations. Lewis encouraged Tolkien to persevere with his Middle-earth writings.A small selection from the many books about Tolkien and his created world:
Owen Barfield
Barfield and C. S. Lewis met in 1919 as students at Oxford University and were close friends for 44 years. "It is no exaggeration to say that his friendship with Barfield was one of the most important in his [Lewis's] life…” The relationship was reciprocated. Almost a year after Lewis's death, Barfield spoke of his friendship in a talk in the USA: "Now, whatever he was, and as you know, he was a great many things, CS Lewis was for me, first and foremost, the absolutely unforgettable friend, the friend with whom I was in close touch for over 40 years, the friend you might come to regard hardly as another human being, but almost as a part of the furniture of my existence.” When they met, Lewis was an atheist who told Barfield, "I don’t accept God!" Barfield was influential in converting Lewis. Lewis developed the concept of two kinds of friends, a first friend with whom you feel at home and agree and a second friend who brings to you a different point of view. He found Barfield's contribution in this way particularly helpful despite, or because of, the fact that “during the 1920s, the two were to engage in a long dispute over Barfield's (and their mutual friend, A.C. Harwood's) connection to anthroposophy and the kind of knowledge that imagination can give us… which they affectionately called 'The Great War'. Through their conversations, Lewis gave up materialist realism – the idea that our sensible world is self-explanatory and is all that there is – and moved closer to what he had always disparagingly referred to as “supernaturalism.” These conversations influenced Lewis towards writing his Narnia series. As well as being friend and teacher to Lewis, Barfield was (professionally) his legal adviser and trustee.