Chapter V: The Heavens Summary and Analysis

Much like the modern world conceives of physical objects "obeying laws," the Medievals spoke, for example, of a stone "desiring" to travel towards the Earth. In neither case, should the metaphor be taken literally. The "desires" or inclinations of physical objects depended upon their elemental make-up—whether their composition included earth, wind, air, or fire, and in what proportions. Earth inclined downwards, for example, while fire inclined upwards. The Medievals also conceived of a fifth element called aether, but it only existed outside of the sublunary sphere; that is, one would have to travel outside of the orbit of the moon to find it.

For the Medievals, the Universe was a series of concentric spheres and Earth was the center. Each planet had its own sphere and the final, largest sphere was where the...