Why is there motion? The stars move, birds move, people move, air moves, even rocks move (when dropped). Why?
In the Physics, Aristotle inquires into natural or movable bodies. The source of their motion is explored. But this mode of inquiry leaves him on the threshold of metaphysics and theology. To look into the causes of motion leads him to investigate a first cause of motion–that is, an eternal, sustaining cause. This new mode of inquiry, followed up in the Metaphysics, leads to an insight not only into motion, but into being itself.
Motion and change, despite their appearances are quite regular. At the atomic, elemental, and cellular level, even up to the symbiotic level of existence, we see something that can be characterized as organization. Accidents, chaos, mutations and collisions are all the result of different levels of organization and causation intersecting. So if we are to ask about the source of motion, we ultimately are looking into the source of all this order.
Completing the Circle
In the climatic book of the Metaphysics (XII), Aristotle returns to the question of the first mover, and he once again deduces that there must be an unmoved mover of the universe. He then concludes that this unmoved mover moves the sphere of the fixed stars. But it causes motion, not by touching, but in the manner of something desirable. The eternal circular motion of the heavens is an imitative expression of longing. The order of the heavens is brought about by the Unmoved Mover, that is, by the Unmoved Mover being an object of desire.
Dante drew upon this conception of the universe when he wrote in his Paradiso of a “love that moves the sun and all the other stars.”
At this point, Aristotle looks directly into the nature of this Unmoved Mover. He discovers what is implicit in the motion of the heavens, that this divine Being is not merely a cause of motion, but of being. But even more radically, it causes being, by being a cause of order, because to be is to be ordered.
The Unmoved Mover is not merely what sets the heavens in motion and thus maintains movement. The Unmoved Mover is the principle of all being in as much as it is the principle of organization-not just that we exist, but the manner in which we exist.
The universe as such could not exist without something maintaining it in motion, but even more so, it could not be what it is without something maintaining it as an ordered array–a cosmos
In The Army or the General?
Aristotle than asks whether the good of the universe is something found in a separate/distinct part, or whether it is in the whole. Or perhaps, he concludes suggestively, it is like an army, in which the order is first and foremost in the general, but also, because of the general in the whole.
This General who contemplates himself is not empty or without order. While the Unmoved Mover does not think of the rest of the universe (unlike the true God), it yet contains the totality of all order, the fullness of all possible arrangement and beauty in the divine simplicity of its everlasting activity.
It is this order by which the universe is governed. And this conclusion brings to a close a long circle which began in the Physics. The first Mover, the efficient cause of motion is revealed to be identical with the final cause of being, that for the sake of which all things live and move.
To investigate the cause of motion is here shown not merely to be a search into a first movement in time, but into the nature of being itself. (Aristotle is not, after all, looking into the first temporal movement, which itself is not a coherent question for him.) For this reason, for him to investigate a first motion is to investigate something far more startling. It is to ask, not simply why things move, by why things are the way they are, ordered, regular, and, yes, even in motion. Thus to ask about motion and order is to arrive at the doorstep of being itself. Natural motion is simply one indication of this startling fact, that existence is itself something dynamic, expressive of arrangement and purpose.
The unity of each being, the unity of the cosmos, the laws which govern nature and even the yearnings of the human heart are due to this Being that maintains motion which is not merely motion, a Being that brings form and matter into harmony, who gives limit and direction to contraries, who makes the causes causes and serve regular ends.
What kind of order are we talking about? What kind of Being. Aristotle permits himself to suggest that this Being is Intelligence itself, that the activity of this intelligence is Life itself, and that such a being is happy, and Good. In the face of such a conclusion, of such order and unity, Aristotle concludes, echoing Homer, “Let there be one Lord!”