The famous tagline for The Highlander movies (movies which became increasingly infamous and cringe-worthy as time passed). If you've seen the trailer for part 1 of Harry Potter and the Deathly Hallows--I admit I've never read a Potter book nor watched any of the films-- , perhaps you noticed one of the slogans: "Only One Can Live." I've been reading Thomas Aquinas on a daily basis for the past few weeks and one "slogan" I've encountered many times in his writings is along the lines that "all things tend to one," or that "Nature is disposed to unity." So when I saw the slogan in the Harry Potter trailer, I was struck by how perennial wisdom surfaces even in the most unexpected places. No one goes to a Harry Potter for lessons in metaphysics--well, perhaps some people go for lessons in "the metaphysics section at Borders" metaphysics--, yet in that slender slogan, they are encountering a fundamental principle of true metaphysics. The quest of scientists for a grand unified theory is a profound reflection of the metaphysical 'instinct' in all things to find unity in the final end of all reality. The highest aim of science is to reach a total, intelligible account of reality, even reality that surpasses humans' perceptual and, indeed, conceptual powers.
This is all a sad instance of man's noetic fallenness, for, in a rectified intellect, the willingness to admit an ultimate account of reality, rooted in principles that surpass spatiotemporal perception and which, of themselves, unalterably account for the contents of reality, should generate a parallel admission of an equally autonomous cause of reality as existing metaphyiscally prior to the spatiotemporal contours of the final account. The convergence of all things to unity--and this unity would of course be absolute and non-contingent, on account of its pure non-composition--, is but the mirror image of their origin from one cause.
The appearance of this principle in something as "fluffy" as Harry Potter reveals how the primacy and ultimacy of the One is not only a metaphysical but also an ethical principle. It is only the dramatic tension of all things converging to unity--"There can be only one"--which makes Harry Potter a genuinely human and humane narrative. A life directed to many disparate ends is a degenerate life, not the life of a hero.