Larger context for LACK in Corpus USbrown_UKbncw/US_brown.txt
This, conjoined with the considerations above, made the circular motions of heavenly bodies appear an almost directly observed fact.
Additional philosophical considerations, advanced notably by Aristotle, supported further the circularity principle.
By distinguishing superlunary (celestial) and sublunary (terrestrial) existence, and reinforcing this with the four-element physics of Empedocles, Aristotle came to speak of the stars as perfect bodies, which moved in only a perfect way, viz. in a perfect circle.
Now what is perfect motion?
It must, apparently, be motion without termini.
Because motion which begins and ends at discrete places would (e.g. for Aristotle) be incomplete.
lack > Circular motion, however, since it is eternal and perfectly continuous, lack s termini.
It is never motion towards something.
lack > Only imcomplete, imperfect things move towards what they lack .
lack > Perfect, complete entities, if they move at all, do not move towards what they lack .
They move only in accordance with what is in their natures.
Thus, circular motion is itself one of the essential characteristics of completely perfect celestial existence.
To return now to the four-element physics, a mixture of muddy, frothy water will, when standing in a jar, separate out with earth at the bottom, water on top, and the air on top of that.