Terminology Tuesday: Chain of being
A key element in the worldview of many ancient, medieval and early modern philosophers, who assumed a principle of plenitude in which beings of every possible type must be actualized, from the lowest to the highest. Thus in the medieval world it was common to think of various entities as possessing different degrees of being, from insignificant bare specks of matter through plants and animals and humans and on to angelic beings and God himself, who possesses the highest possible degree of being. The universe is a vast hierarchy of beings, and it is good that all positions in the hierarchy are filled. See also Neo-Platonism.
Evans, C. S. (2002). Pocket Dictionary of Apologetics & Philosophy of Religion (pp. 22–23). Downers Grove, IL: InterVarsity Press.