Re: The "Classic" Elements
"In his stoichiology Aristotle adopts the four elements, or radical principles, which Empedocles introduced. He teaches, however, that the celestial space is filled with a body different from the four elements. This seems to be the part assigned by him to ether.{64} Ether, then, is neither a fifth element entering with the other four into the constitution of the terrestrial world, nor, as is sometimes maintained, an undifferentiated substratum, like the apeiron of Anaximander, from which the four elements originated. It is the constituent of celestial bodies. The natural motion of ether is circular; that of the other elements is upward or downward, according as they are naturally endowed with lightness or with heaviness. It is hardly necessary to remark that until Newton's time there existed the belief that each particular body moved towards its own place, upward or downward, in virtue of the light or heavy elements which it contained." http://www2.nd.edu/Departments//Maritain/etext/hop11.htm