Apr 04 2008
The Existence of God (A Simple Summa)
What follows is from St Thomas Aquinas’ Compendium of the Summa Theologica. It is a simplified form of the five proofs for the existence of God, which St Thomas treats of in the Prima Pars (first part) of the Summa Theologica, Question 2, which can be read HERE. St Thomas treats of the subject in a much fuller fashion in the Summa Contra Gentiles, chapters 3-13 which can be read HERE (see especially chapters 10-13)
That God exists is in itself a self-evident truth; but it is not so to us who do not see the Essence of God; and it requires to be proved by those things which are more known to us as regards ourselves and less known in their nature, that is, by effects. Although we know God in a general way, we do not therefore know Him absolutely. It is possible to demonstrate the Existence of God by effects, which are more known to us than their cause, for effects, which are more known to us than their cause, for effects being granted, a pre-existing cause there must be; and we call this demonstratio quia, not propter quid, for not even by effects do we know the Essence of God.
The Existence of God may be shown by five proofs. The first is drawn from the principle of motion. It is evident to our senses that motion exists. Whatever is moved must be moved by some external agent. Nothing is moved unless it is in potentiality (in potentia) to its term of motion. Motion is made accordingly as things are changed from the potential to the actual, and this requires some actual agent to move them from the potential state. Since it cannot be that anything should be both potential and actual as regards the same order, it follows that the mover and the moved cannot be identical. Thus, not to go on indefinitely, we must come at last to a First Cause immovable of motion; and there we find God.
The Second Proof consists in the order of Efficient Causes in sensible objects. Nothing can be its own efficient cause, for then it would exist before itself. In every order of being the first is the cause of the intermediate, and this latter the cause of the ultimate; so that if the cause e removed the effect ceases to be, and if the first is gone there can e neither the intermediate nor the ultimate. Hence, not to proceed indefinitely, there must be a First Efficient Cause; and there too we find God.
The Third Proof is taken from possible and necessary things. Some things may be or not be; they are possible, as they are subject to generation and decomposition; but everything could not be always thus, for what is not necessary at some time is not. If, therefore, all things may possily not be, at some time there must have been nothing; and if this be true even now, there would be nothing, for what is not can only exist by that which is. All things, therefore, are not mere possibilities in their origin; there must exist some necessary thing. But whatever is necessary, either has cause for its necessity or it has not; and, not to proceed indefinitely, as regards necessary things with a cause for their being necessary, we are obliged to postulate something necessary in itself with no cause for its necessity, but itself the cause to other things of their necessity; and this is God.
The Fourth Proof proceeds from our finding some things better than others. A thing is said to be more or less as it approaches to that which is called the most. There exists, therefore, something which is best and truest, the source to things of all goodness and truth, and of all their other perfections; and this we call God.
The Fifth Proof is drawn from the idea of government. Some things are without understanding, yet they work for an end, because often and always they work in the same way to obtain the best end; hence it is evident that they attain the end not by chance, but by intention; and since they must act towards the end not by their own but by some one’s knowledge, they reach the end because they are directed by an Intelligent Being. There must, therefore, be such an Intelligent Being Who directs all natural things to their end; and Him we call God.
For further reading: HE WHO IS by Walter Farrell
