The great chain of being (Latin: scala naturae, literally “ladder or stair-way of nature”), is a concept derived from Plato and Aristotle, and developed fully in Neoplatonism. It details a strict, religious hierarchical structure of all matter and life, believed to have been decreed by God. The chain starts from God and progresses downward to angels, demons (fallen/renegade angels), stars, moon, kings, princes, nobles, men, wild animals, domesticated animals, trees, other plants, precious stones, precious metals, and other minerals.
The Chain of Being is composed of a great number of hierarchical links, from the most basic and foundational elements up through the very highest perfection, in other words, God.
God, and beneath him, the angels, both existing wholly in spirit form, sit at the top of the chain. Earthly flesh is fallible and ever-changing: mutable. Spirit, however, is unchanging and permanent. This sense of permanence is crucial to understanding this conception of reality. It is generally impossible to change the position of an object in the hierarchy. (One exception might be in the realm of alchemy, where alchemists attempted to transmute base elements, such as lead, into higher elements, either silver, or, more often, gold; the highest element.)
In the natural order, earth (rock) is at the bottom of the chain: this element possesses only the attribute of existence. Each link succeeding upward contains the positive attributes of the previous link and adds (at least) one other. Rocks, as above, possess only existence; the next link up, plants, possess life and existence. Animals add not only motion, but appetite as well.
Man is both mortal flesh, as those below him, and also spirit as those above. In this dichotomy, the struggle between flesh and spirit becomes a moral one. The way of the spirit is higher, more noble; it brings one closer to God. The desires of the flesh move one away from God. The Christian fall of Lucifer is thought of as especially terrible, as angels are wholly spirit, yet Lucifer defied God, the ultimate perfection.