A prevalent notion throughout much of human history has been that the human being (the microcosm) was a miniature replica of the Universe (the macrocosm); the Universe was then seen as geocentric, so the perceived relationship was in fact with the Earth (and its components) and the more visible celestial objects. Thus human eyes equated with the sky's two great lights – the Sun and Moon – and likewise bones with rocks, hair with vegetation, the pulse with the tides, etc. Even into the 18th century the notion inspired ideas that the Earth itself might be a living organism; "When the World Screamed" by Arthur Conan Doyle is a very late story with this premise.
A related idea was that there was a "chain of being" that ran in ascending order of biological complexity from fossils and the simplest "animalcules" up to humanity and then beyond, to the Angels and God. Were any link in this chain to be missing, the set-up of the Universe would be impossible; e.g., were there no such creature as a dog, no creature more biologically complex than a dog could exist. Thus the importance of humanity was obvious: were there no humanity, there could be neither angels nor God.
Fantasy often draws on these notions, but probably often without the awareness of the author. The version most often encountered is the Aristotelian one that, though the great may be observably entirely different from the small, there can nevertheless be a one-to-one relationship between their constituent parts. (This is the idea at the core of the theory of transubstantiation: the bread clearly does not magically turn into a gobbet of flesh, yet it is Christ's flesh because the one-to-one relationship makes the two identical.) Thus the king can become the Land, and his lack of personal Healing may turn his country into a Waste Land. [JG]