The Ainulindalë contains what is undoubtedly one of the best literary treatments of the relationship of divine sovereignty, providence, or predestination on the one hand, and creaturely freedom and the so-called “problem of evil” on the other (indeed, even measured as a philosophical statement of these issues, the Ainulindalë doesn’t fare too badly). In the early version from The Book of Lost Tales, the Creator Ilúvatar’s explanation to the diabolus Melko(r) concerning the former’s supremacy and purpose over all that transpires is even more explicit and expanded (even if somewhat less poetical). In addition to the logos and pathos of the passage, it is remarkable also to bear in mind it’s author’s ethos. The following was penned sometime between 1918 and 1920 (during Tolkien’s stint working on the Oxford English Dictionary), and hence within a couple of years of when Tolkien had directly experienced the horrors of the Great War and in which, as he himself would later observe, all but one of his closest friends had been killed:
“Thou Melko shalt see that no theme can be played save it come in the end of Ilúvatar’s self, nor can any alter the music in Ilúvatar’s despite. He that attempts this finds himself in the end but aiding me in devising a thing of still greater grandeur and more complex wonder: –for lo! through Melko have terror as fire, and sorrow like dark waters, wrath like thunder, and evil as far from my light as the depths of the uttermost of the dark places, come into the design that I laid before you. Through him has pain and misery been made in the clash of overwhleming musics; and with confusion of sound have cruelty, and ravening, and darkness, loathly mire and all putrescence of thought or thing, foul mists and violent flame, cold without mercy, been born, and death without hope. Yet is this through him and not by him; and he shall see, and ye all likewise, and even shall those beings, who must now dwell among his evil and endure through Melko misery and sorrow, terror and wickedness, declare in the end that it redoundeth only to my great glory, and doth but make the theme more worth the hearing, Life more worth the living, and the World so much the more wonderful and marvellous, that of all the deeds of Ilúvatar it shall be called his mightiest and his loveliest.” (LT 55, emphasis added)
The Flame Imperishable 