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Aristotle: the Prime MoverAristotle believed that all movement depends on there being a mover. For Aristotle, movement meant more than something travelling from A to B. Movement also included change, growth, melting, cooling, heating…etc.
Just like his predecessor Heraclitus, Aristotle recognised that everything in the world is in a state of flux.
Aristotle argued that behind every movement there must be a chain of events that brought about the movement that we see taking place.
Aristotle argued that this chain of events must lead back to something which moves but is itself unmoved. This is referred to as the Prime Mover.
In Aristotle’s view change is eternal. There cannot have been a first change, because something would have to have happened just before that change which set it off, and this itself would have been a change, and so on.
In his book Metaphysics (literally after physics), Aristotle calls this source of all movement the Prime Mover. The Prime Mover to Aristotle is the first of all substances, the necessary first sources of movement which is itself unmoved. It is a being with everlasting life, and in Metaphysics Aristotle also calls this being ‘God’.
The Prime Mover causes the movement of other things, not as an efficient cause, but as a final cause. In other words, it does not start off the movement by giving it some kind of push, but it is the purpose, or end, or the teleology, of the movement. This is important for Aristotle, because he thought that an effective cause, giving a push, would be affected itself by the act of pushing. Aristotle believed the prime mover causes things to move by attraction in much the same way that a saucer of milk attracts a cat. The milk attracts the cat but cannot be said to be changed in the process!
Isaac Newton came to the same conclusion in his Third Law of Motion, when he said that ‘action and reaction are equal and opposite’. Aristotle was keen to establish that the Prime Mover is itself Unmoved, or unaffected, otherwise the whole concept would break down. The Final Cause causes movement as the object of desire and love. If God did give things an initial push then he himself would be changed. Instead God draws things to himself and remains unaffected. The stars and the planets move out of a spiritual desire to imitate God. They do this by moving in eternal circles.
Aristotle believed that God exists necessarily, which means that God does not depend on anything else for existence. He never changes or has any potential to change, never begins and never ends, and so is eternal. Eternal things, Aristotle claimed, must be good; there can be no defect in something that exists necessarily, because badness is connected with some kind of lack, a not-being of something which ought to be there, an absence of the ‘actuality’ that Aristotle thought God most perfectly has.
Aristotle argued that the Prime Mover had to be immaterial. It could not be made of any kind of stuff, because matter is capable of being acted upon, it has potential to change. Since it is immaterial, it cannot perform any kind of physical, bodily action. Therefore, Aristotle thought, the activity of the Prime Mover, God, must be purely spiritual and intellectual. The activity of God is thought.
But what does God think about it? God could not think about anything which caused him to change in any way; nothing which could affect him, or react, or even change him from not-knowing to knowing. Aristotle concludes that God thinks about himself only. Nothing else is a fit subject. He even defines God as ‘thought of thought’, or ‘thinking about thinking’. At the end of this line of argument, Aristotle comes to the conclusion that God knows only himself; so he does not know this physical world that we inhabit, he does not have a plan for us, and he is not affected by us.
Aristotle’s concept of the Prime Mover found its way into the medieval theology of Thomas Aquinas and his cosmological proof for the existence of God. Likewise, Aristotle’s teleological arguments found their way into Aquinas’ Natural Law.