The nice thing about organized religion as opposed to disorganized religion is that the former at least tries to be objective and rational, whereas the latter is unashamedly biased and uninterested in rational and empirical proofs. Indeed, they prefer emotional proofs; a crude mysticism appeals to what we might call the ‘disordered religious mind.’
St. Thomas comes to the front during the High Middle Ages, doing much to eradicate excessive forms of mysticism and rationalism, via Aristotle’s logic, but also his empiricism. It was a huge task; it was upon him to synthesize the entire Christian religion through the Aristotelian philosophy. Prior to St. Thomas of Aquino, no one had really fielded a sound theological theory based on Aristotle. The Church was still meddling with various forms of Platonism and Augustinian philosophy.
St. Thomas, wasn’t so much innovating anything new, rather he was taking very old concepts from the Greeks and hackneying them out for Parisian scholasticists, on the field of Catholic theology. The concept of a necessary being goes back to the pre- Socratics. However, this old game gets a second wind with St. Thomas.
Using the Aristotle’s organon and his philosophy of causes, St. Thomas crafts an argument which is popularly called ‘The Five Ways.’ It seems to be a single argument, one of causation; however, it’s five ways to prove that God exists, i.e. that God is a necessary being. Again, it proves ‘that God is’ not ‘what God is;’ these arguments do nothing to prove the existence of the Christian God, beyond that God is a single being as opposed to multiple gods, which Christianity professes to be the case.
The ‘first way’ to prove the necessary existence of God is the argument from motion. We know empirically that some things are in motion, and according to Aristotle things move when ‘potentiality’ of movement becomes ‘actuality.’ That is to say, wherever [X] causes [Y] to be f, it is because [X] is actually f and [Y] has the potentiality to be f. So, as the scholasticists would say, only something which is motion in the ‘act’ can cause something potentially in motion to be actually in motion. Further, nothing can be both in potentiality and actuality in the same instant, in the same way, and because of this nothing can move itself. Therefore, anything that is in motion was put into motion, or moved, by something else. That pattern of moving, or more specifically the pattern of ‘being caused to move’ can’t go on infinitely; that is an impossibility for obvious reasons. These premises, if true, necessitate an ‘unmoved mover,’ as I believe Aristotle termed it, a being that was not put into motion by anything and yet causes all things to be in motion. This necessary being St. Thomas asserts is understood by everyone to be God.
The ‘second way’ is constructed in a nearly identical fashion to that of the ‘first way’ and deals with efficient causes. However, because of the similitude of the arguments it is superfluous to demonstrate the argument. So, I will simply proceed to the Dumb Ox’s (St. Thomas) ‘third way.’
The ‘third way’ to prove that God is a ‘necessary being’ is said to be a reductio argument. The argument begins by pointing out that ‘contingent beings’ are evident in nature, i.e. such beings as do not necessarily exist. In point of fact, this would include all beings that we are empirically aware of, and St. Thomas asserts this fact. Now, for each contingent being that exists, there is a time in which it does not exist (which is better to say than a time in which it did not exist). So, it is impossible for these contingent beings to always exist. For instance, we can look at the extinction and destruction of individual and particular contingent things, and discern the possibility of the same for all contingent things. Therefore, it is plausible that there was a time when no contingent things existed. Hence, there would have been nothing to bring contingent things into existence and if that were the case, then nothing would exist. However, this is absurd and a contradiction, the argument has been reduced to its most absurd point. So, it cannot be that every being is a contingent being, because it leads to a contradiction. In this we see, and St. Thomas would say that we know, that there is such a being that exists which is necessary, that is not caused to be by anything, but causes all things to be. This necessary being, St. Thomas asserts is God.
The ‘fourth way’ to prove the necessary existence of God is an argument of gradation. It is perhaps the simplest of the arguments which might be called ‘convincing,’ and it starts off by simply pointing out that some things are better and worse than others. In order to denote degrees of ‘better’ and ‘worse’ when talking about beings, with any validity, it is necessary to have a concept of the most extreme example. The most extreme case is the teleological cause of things which are the same. Apply this principle to ‘perfection’ and ‘being,’ and it follows necessarily that there is a primary cause of all things perfect, and all things that have being. This necessary being, St. Thomas’ asserts, is called God.
The ‘fifth’ way is the least convincing argument and most subjective, or at least I find it to be so, and it does not interest me in the slightest. So, I will not hazard an explanation of the fifth argument, other than that it is an argument from design.
"Every art and every inquiry, and similarly every action and choice, is thought to aim at some good; and for this reason the good has rightly been declared to be that at which all things aim." ~Aristotle~