To the assertion that the circular movement is a corporeal movement,
it might be objected that one can see that every body, even fire,
moves in a straight line. However, the fire moves in a straight line
only till it reaches the place assigned to it by the universal order
(it constitutes the heavens, which are its proper place). By virtue of
this order its nature is permanent, and it moves towards its assigned
location. Why then does the fire as soon as it has arrived there, not
abide there quiescently? Because its very nature is constant movement;
if it went in a straight line, it would dissipate; consequently, it
necessarily possesses a circular motion. That is surely a providential
arrangement. Providence placed fire within itself (because it
constitutes the heavens, which are its location); so that, as soon as
it finds itself in the sky it must spontaneously move in a circle.