The notion of the unmoved mover is presented in Aristotle’s Book XI of his Metaphysics.
Aristotle’s most basic argument is that everything that is in motion is moved by something else. However, there cannot be an infinite cause of things that are moving. At some point, there has to be an ultimate cause.
This ultimate cause of motion shouldn’t be moved. Otherwise, it was also caused by something else. It isn’t made of physical matter. Otherwise, it will change and, therefore, move. It also necessarily lacks Potentiality. Therefore, it is simply Actuality.
The implications of the existence of an unmoved mover is profound. First, it simply means I did not come in this life by my own accord (We did not choose to exist). I was brought here by someone or something that is way more powerful than myself. And the nature of this thing or person is filled with mystery. The answers about its nature are not intuitive. They have to be pondered about. But answers don’t have to be clear or final. The awe that the mystery produces is enough to move us to embrace intentional living (i.e., appreciate everything and every moment we are alive and let that appreciation guide us to do the most important action).
References
Aristotle—The unmoved mover | Britannica. (n.d.). Britannica. Retrieved August 25, 2022, from https://www.britannica.com/biography/Aristotle/The-unmoved-mover
The way in which Aristotle seeks to show that the universe is a single causal system is through an examination of the notion of movement, which finds its culmination in Book XI of the Metaphysics.
Aristotle’s fundamental principle is that everything that is in motion is moved by something else.
He then argues that there cannot be an infinite series of moved movers.
This series cannot go on forever, and so it must come to a halt in some X that is a cause of motion but does not move itself—an unmoved mover.
It must lack matter, for it cannot come into existence or go out of existence by turning into anything else.
It must also lack potentiality, for the mere power to cause motion would not ensure the sempiternity of motion. It must, therefore, be pure actuality (energeia).
Such a mover could not act as an efficient cause, because that would involve a change in itself, but it can act as a final cause.
Aristotle is prepared to call the unmoved mover “God.”