Then, since the fire of the sidereal system has attained its goal, why does it not stay at rest?
Evidently because the very nature of fire is to be mobile: if it did not take the curve, its straight line would finally fling it outside the universe: the circular course, then, is imperative.
But this would imply an act of providence?
Not quite: rather its own act under providence; attaining to that realm, it must still take the circular course by its indwelling nature; for it seeks the straight path onwards but finds no further space and is driven back so that it recoils on the only course left to it: there is nothing beyond; it has reached the ultimate; it runs its course in the regions it occupies, itself its own sphere, not destined to come to rest there, existing to move.
Further, the centre of a circle [and therefore of the Kosmos] is distinctively a point of rest: if the circumference outside were not in motion, the universe would be no more than one vast centre. And movement around the centre is all the more to be expected in the case of a living thing whose nature binds it within a body. Such motion alone can constitute its impulse towards its centre: it cannot coincide with the centre, for then there would be no circle; since this may not be, it whirls about it; so only can it indulge its tendence.