If anguish were visible, almost the whole of this benighted planet would be enveloped in a dense dark vapor, shrouded from the amazed vision of the heavens! And the products of it all will be mainly evil - historically considered. But the historic version is, of course, not the only one. All things and deeds have a value in themselves, apart from their "causes" and "effects." No man can estimate what is really happening sub specie aeternitatis. All we do know, and that to a large extent by direct experience, is that evil labours with vast powers and perpetual success—in vain: preparing always only the soil for unexpected good to sprout in.
J.R.R. Tolkien, Letters (Letter 64, 10 April 1944 to his son Christopher), p. 76