Turning from the eternal entities in the celestial realm to the world of coming-to-be and passing-away, Aristotelian doctrine assigns to each of the four sublunary elements a natural place in accordance with its absolute or relative lightness or heaviness. These elements, forming concentric layers of fire, air, water, and earth in descending order, are involved in a continuous cycle of transformation into one another, by virtue of possessing one of the active qualities of hot and cold and one of the passive qualities of dry and moist. The distribution of these primary qualities is such that earth is dry and cold, water cold and moist, air moist and hot, and fire hot and dry.
An interesting development in some Late Byzantine texts is the idea that the sharing in each primary quality by neighboring elements is responsible for preserving the unity of the world. This idea appears full-fledged in Blemmydes, Epitome physica 11.22, and later reappears in Choumnos, De natura mundi. Its proximate source is probably Basil the Great, Homiliae in Hexaemeron 4.5, another important source text for Byzantine natural philosophy. In Basil, however, it is only sensible compounds that are assigned two primary qualities; the elements have only one, and their connection is left unexplained. Blemmydes enhances the idea by insisting on the Aristotelian theory assigning two primary qualities to each of the elements, so that earth essentially connects with water, and so on. Possibly the idea of shared primary qualities was linked in Blemmydes’ mind with that of natural places, each element having its natural place between those two elements with which it shares each of its primary qualities (cf. Aristotle, Physics 4.5 and De caelo 4.3 with Simplicius, InPhys. 597.16-20 ).
It is against this background that one must view Gregoras’ denial, in the Phlorentius, that the absence of shared qualities would pose a threat to the unity of the world, since all bodies share in weight. Some of Gregoras’
Statements in the dialogue seem to suggest that he understood the problem as that of securing spatial cohesion, which is indeed a classic problem for those who believe in extracosmic void.
World History
