[quote="Marc_Anthony, post:1, topic:295994"]
Candide West in this thread,and specifically this post, (forums.catholic.com/showpost.php?p=9677050&postcount=348) raised an interesting question.
Let's assume for the sake of argument that the Five Ways prove what they intend to prove. Why do we assume all five proofs prove one God? Wouldn't the five proofs actually prove five different "gods", each responsible for some different aspect of the world?
I'll put it another way. We know that the first proof proves that there must be a Prime Mover-a thing that sets everything else in motion.
-The second proof defines God in terms of efficient causality; God is the "First Cause", not the "Prime Mover". So God makes everything else move (like a car rolling) in the first proof, but God causes everything (like a fire lighting) in the second proof. They're closely related, but different. So now we know that God is the Prime Mover and the First Efficient Cause.
-The third proof defines God as the Necessary Being. In this proof it is said that God must cause everything else to exits. So here we learn that God also has the ability to create literally anything not logically contradictory.
-The fourth proof defines God as the Perfect Being. God is the "measuring stick" for all that is "perfect" (things like goodness, knowledge, etc...it's a concept specified more in detail in the rest of the Summa). At any rate, that would mean he is omniscient (maximum knowledge), omnipotent (maximum power), and omnibenevolent (maximum goodness).
-The fifth proof defines God as what I'll refer to as the "Intelligent Director". Basically since things with no intelligence act the same way nearly every time (i.e., a match when struck on the right surface almost always produces a flame), there needs to be something that "directs" them, called God. So we know that God has the power to will things already in existence.
How is it proven that each proof refers to the same being? Why can't each proof refer to different beings, all of which exist?
I'm curious to see the answers. It was never a question I seriously considered.
One striking feature about the five proofs is that every proof is very interrelated. There's a lot of overlap. If you prove God one way many times you're over half way there to proving God in another way. Indeed, sometimes the distinctions in-between the proofs were so subtle that it was heard for me to come up with a specific descriptor for each definition proven.
Still, I'm not sure of the exact steps to get from point A to point E.
Well, on one hand, it seems rather simple, the prime move and the first cause could not be two beings co-existing. Why? Go either direction, start from the "First Cause". As Aquinas tells us, "There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself", hence how can the prime move exist if the First Cause did not cause him to exist. But if the First Cause created the prime mover, how can one say the prime mover put all of creation in motion?
Ok, I will admit, the above is the wrong approach to take for us amateurs. A better way is to see how Aquinas answers your question:
Go to question 3 of the Summa, "The Simplicity of God". ww.newadvent.org/summa/1003.htm . It follows directly after his existence proof. In many ways, this is better than his proofs of God. These articles tell us what we can know about God through our reason. On these Aquinas explicitly addresses the question you ask in various ways:
1.Is God a body?
2.Is He composed of matter and form?
3.Is there composition of quiddity, essence or nature, and subject in Him?
4.Is He composed of essence and existence?
5.Is He composed of genus and difference?
6.Is He composed of subject and accident?
7.Is He in any way composite, or wholly simple?
8.Does He enter into composition with other things?