Aristotle recognised that everything in the world is in a state of flux or motion and 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 such as growth, cooling and heating. This movement from potentiality to actuality lead Aristotle to the conclusion that there are stages in causation. He called these the four causes: Material, Formal, Efficient and Final causes, a theory that explains how everything that is observed in the world appears to have existed through cause and effect. These four causes can encompass an objects complete description, such as what it's made of, what it looks like, what made it and its purpose.
The Causation theory is the basis for much of Aristotle's work, including Metaphysics. Which clearly define Aristotle's way of studying the world around him, which is empirical and observant of what we can see and know; a trait completely different to what Plato taught. The Final Cause differs greatly from the others because it describes something's ultimate purpose, not just a material viewpoint, and God (or the Prime Mover) has to be our Final Cause as he alone is perfection, and everything good that we do is to seek perfection. St Thomas Aquinas would use this notion as the first of his Five Ways; it is an important element in his Cosmological Argument.
Aristotle argued that there are four causes, the first cause being the material cause of an object, this is what the object is made of; the material cause of a wooden chair is wood as this is what it is composed of.The characteristic of an object is the Formal cause, the pattern, model or structure upon which a thing is made, a wooden chair has four legs and is shaped in a way that someone can sit on it. The efficient cause is the means or agency by which a thing comes into existence, the force that affects an object, the builder or sculptor is the efficient cause of the chair.
Alone, the formal, material and efficient explain what the object is and how it came into being, but that is that. They do not explain what the object does, Without the Final Cause, this theory does not explain why, but only how. The Final Cause therefore explains the purpose or telos of an objects existence, and what it is for according to Aristotle, everything has a purpose, including nature. Whether the purpose of a creature or plant is useful to man is irrelevant. For example, bees are useful to us because they make honey, but that does not mean that it is their purpose, their purpose perhaps could be to pollinate flowers. The Final Cause is therefore the most important cause because it describes the object in a non-materialistic way and gives us an idea on why it is there.
What separates the Final Cause further from the three other causes is the fact that Aristotle's idea of God is the Final Cause of change and movement, and therefore God is the Final Cause of us. Aristotle's description of God arises from the idea of movement having a mover. Any kind of change has to have been made to happen by something or someone. For example an object is capable of being heated, such as coal, or moved, such as a football, has to be heated or moved by something itself actually hot (like fire) or moving (like a footballer’s boot).
Therefore, Aristotle argues that the beginning of the chain which leads to the change must itself be unchanging; it must be actual and not potential. There must be an unmoved mover, the Prime Mover, itself unmoved by something else but attracting all matter by way of charge to actualise its potential. Aristotle says that this eternal movement and change had to have started off with an unmoved mover, or Prime Mover. This is something that is a mover but does not move itself. According to the laws of physics, one cannot simply move something without moving itself, meaning that this Prime Mover is not the Efficient Cause of eternal movement.
Aristotle believed that, the Prime mover who is the final cause exists necessarily, which means that God does not depend on anything else for existence.It 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 beleived that the Prime mover most perfectly has. Therefore, the Prime Mover has to be immaterial. It cannot be made of any kind of substance, 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, the activity of the Prime Mover or God, must be purely spiritual and intellectual.God could not think about anything which caused him to change in any way, 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’. Aristotle comes to the conclusion that God knows only himself; so it does not know this physical world that we inhabit, he does not have a plan for us, and is not affected by us,it is impersonal.
To conclude, the Prime Mover (for Aristotle) or God (for Aquinas) is the final cause of the universe. Aristotle believed that all movement (by which he meant change) requires a mover , something external that causes change but is itself unchanged or unmoved. This eternal change is the final source of all movement. This is what Aristotle calls the Prime Mover. The Prime Mover causes the movement of things, not as an efficient cause, but as the final cause. In other words, it does not start of movement by giving it a push, but is the purpose, goal or the teleology of the movement. Everything has a desire for the Unmoved Mover or Prime mover; therefore he is necessary and does not depend on any contingent being.