All movement is for the sake of perfection. This is because the perfection of anything is its goodness, and goodness is the fulfillment of some potency according to the act to which it is ordered. All created goodness, though, is good insofar as it participates in the uncreated or divine goodness. The divine goodness, then, is that for the sake of which all things move.
“For in him we live, and move, and have our being; as certain also of your own poets have said, For we are also his offspring” (Acts 17:28).
All things participate in the divine goodness inasmuch as they exist and move, but since the motions and activities of creatures differ according to their natures, each creature attains to the divine likeness in its own way. For example, all living creatures attempt to maintain themselves in perpetual existence both individually and specifically, meaning through the reproduction and care of offspring. In this way, creatures imperfectly imitate the eternity of God.
Atop the hierarchy of creation rests a creature whose perfection exceeds all other physical beings. This creature attains to the divine likeness in a unique and more perfect way than anything else. Man, the rational animal, is this creature.