Proving the existence of God: St. Thomas Aquinas five ways

By NZAU MUSAU

Writing in Summa Theologiae (handbook of theology), St. Thomas Aquinas demonstrates that God exists by analyzing five phenomena which indicate to the necessity of his existence. He does this by drawing attention to a certain phenomena’s (five of them) whose relative, dependent and caused character is evidenced. In all five, he demonstrates that the actual reality of the original causer of these phenomena cannot be explained by invoking the explanation of an infinite series of contingent causes. The long and short of it, is that, God can only be the person or entity behind these phenomenon.

1. The first way: Cosmological argument for God’s existence

St. Aquinas argues that this is the most apparent as the phenomenon of change/movement which is considered here as perceptible through the senses. The universe and the objects within it contain change. Girls become women, seeds become trees, leaves wither and young men become old.

Each such a phenomenon however points out to something else besides the particular change. This is to say it points to a certain origin of the change or potency. Change must necessarily have an origin as it cannot cause itself. Another phenomenon is necessary in order to cause this change, St. Aquinas implies.

When it is agreed that the every action/move has a cause/mover, a series of causes/ movers is established which St Augustine says cannot go infinitely. There must be the first mover and anything else is unthinkable. This first mover/cause is itself unmoved/uncaused and is the origin of all change and motion. St. Aquinas says that this is what people call God.

This way of proving God’s existence has however been challenged in a number of ways among them being that change does not necessarily have to be instigated by something else (cannot things change on their own?) and that change does not necessarily have to have a starting point (cannot the universe be infinite in the sense that it does not have a starting point?). Also, critics have postulated that the first cause/mover need not necessarily be God as claimed by St. Aquinas (cannot this first cause/mover be anything else apart from the Christian God?).

2. The second way: Causal argument for God’s existence

Largely corresponding to the cosmological argument, this causal argument for God’s existence however builds on the connection between cause and effect. Every effect of a cause points back to the cause which points to another cause and so on.

The fundamental phenomenon here is that of efficient causality which is subordinated by other causes. There is no known case (neither is it possible) in which a thing is found to be the efficient cause of itself. St. Aquinas proceeds to argue for a foundation in a principal efficient cause of itself which would otherwise be before itself and therefore absurd.

With this argument, St. Aquinas disapproves as absurd the principle of progression to infinity. He says any attempted explanation of this principle will only create a colossal edifice of inadequate causes. In such a case, there would be no first efficient cause nor there ultimate effect or any intermediate efficient causes. Moreover, to take away the cause is to take away the effect. His conclusion is that there necessarily is a first efficient cause which is God.

3. The third way: Argument for God’s existence based on necessity

St. Aquinas third argument is based on the two concepts of possibility and necessity. It is found that in nature, things are possible to be or not to be. Since there were once not, it is impossible that they will always be for that which was not at one time is not.

If therefore all things came to be according to St. Aquinas, it means at one point there was nothing in existence. This he says would be absurd since all things begin to exist at the instigation of something else already existing. Also if this (that at some point in time there was nothing in existence) were to hold true, there would be nothing in existence to this date. This is not true since things already exist.

His argument here is that there must be one thing, one being whose existence is necessary. This thing would be opposed to the things already in existence whose necessity is caused by other things and as already proved above, this (the chain of necessitation) cannot go on to eternity. We cannot therefore help but admit the existence of some being having of itself own necessity which is independent of any other and which is the origin of all necessitation. This is what is known to men as God.

4. The fourth way: Argument for God’s existence based on the idea of a highest degree of perfection and of being

St. Aquinas bases this on the gradation which is found in things. We see all that exists is more or less perfect and has more or less being. This more or less, St. Aquinas argues, is predicted according to the extent to which they resemble in some way to something which is the maximum.

For instance, someone is said to be noble inasmuch as he nearly resembles that which is noblest. So that in every true thing, there is the truest, every noble the noblest and every great the greatest.

This reasoning point’s beyond the earthly towards something that is perfect and that is absolute being- and this is what is called God. This is the thing which is to all being the cause of their being. It is also the paragon of perfection, the chief embodiment of the good.

5. The fifth way: Teleological argument for God’s existence

This final argument is taken from the governance of the world as observed by St. Aquinas. He postulates that a critical look into the things in existence, order will be observed or even experienced. The universe appears to be well ordered or structured. Even things that lack knowledge appear to act for an end and to the best result.

They achieve their end not by chance but by design. The design aspect is deduced from the fact they always appear to act always or nearly always, in the same way so as to obtain the best result. For example, the earth which has no known knowledge of its own is constantly spinning in its own orbit and does not deviate or move closer to the sun.

This way, it sustains life which is most likely its purpose as designed. St. Aquinas argues that whatever lacks knowledge (as the earth does) cannot move towards an end, unless it is directed by some being endowed with knowledge and intelligence. An arrow cannot direct itself unless an archer does so.

This order in the world and its many subtle connections point to a fundamentally rational and good design. And since this design is not obviously the work of man who himself is amazed by it and in fact seeks to understand it, it can only be the work of a greater rational spirit which not only designs but also actualizes it in the universe. This, according to St. Aquinas, is what we call God.


Bibliography

1. Ten great works of philosophy, Robert Paul Wolf, Signet Classic Printing Press, March 2002.

2. A history of western thought, Gunnar Skirpekk and Nils Gilje, Scandinavian University Press, 2000.

3. A history of medieval philosophy, Battista Mondin, Theological Publications in India, 1998.