Lewis, one of Tolkien's closest friends until Lewis's death in 1964, counseled against making The Silmarillion a "public" work. He disliked the shallow enthusiasm for The Lord Of The Rings among younger readers who had obviously missed its profound central message, and recoiled at the suggestion that Tolkien was creating a new religion, for the obvious reason. That having been said, Lewis was delighted by, and in some ways a participant in, Tolkien's ongoing act of creation, as one can see from the references to it in his novel That Hideous Strength.
The Silmarillion was finally published in 1977, more than three years after Tolkien's death. Christopher Tolkien, who performed the final editing and collation of stories to be included in the volume, was apparently acting on his father's wish, but earlier correspondence between Tolkien and Lewis indicates Tolkien's misgivings about the matter, both out of concern for Lewis's arguments and because the fantasist was, for a time, concerned about looking like an obsessed nut.
(An aside: Did you know that Lewis's hero Elwin Ransom, the central figure in Lewis's Space Trilogy, was patterned on Tolkien? Lewis felt he owed a great debt to Tolkien, who had persuaded him into Christianity and helped to nurture Lewis's own fictional gift. In return, he cast a Tolkien-like figure as a world-savior in his own books.)
Ironically, The Silmarillion diverged greatly, more so than The Lord Of The Rings, from Tolkien's original reasons for writing the books. Tolkien was a student and enthusiast of language, and the invented languages (i.e., Elvish, Dwarvish, etc.) he stippled his creation with were the great pride of his life. His fantasies were originally his way of giving his linguistic creations to voices that would use them. Yet the two "finished products" he issued were stripped of the bulk of what must have been the dearest part of his labors -- the use of the languages themselves by their intended speakers.
Freedom, Wealth, and Peace,
Francis W. Porretto
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