Summa Theologiae
The Summa Theologiae of St. Thomas Aquinas is justly one of the famous works of Christendom. Yet this book, meant for beginners in the ages of Faith, can seem overwhelming today. We give here an introduction to the Summa by Fr. Albert, a son of St. Dominic, in the hope of making this important work more accessible to modern readers.
PART 3
God’s existence: Do we need to prove it? Can we prove it?
In the very first part of his Summa, St. Thomas treats of the being of God before going on to speak of His causality. The first question he asks regarding God’s being is whether He has being or not. This is, obviously, where we must begin, for if God doesn’t exist then there is nothing to talk about. Theology would have no point because it would have no object. This is, in fact, the order followed in all sciences, for it must first be established that their object exists before going on to treat of what it is.1
God’s existence needs to be proved
Some people in St. Thomas’s time thought that it was immediately obvious that God exists, and that there was thus no need to prove it. This is why he begins this question on the existence of God with a little article that shows that it does indeed need to be proved. The first proof he gives of this is the simple fact that some people deny the existence of God, as it says in the Psalm: “The fool said in his heart, ‘There is no God’” (Ps. 52:1). It is possible, then, to deny God’s existence, although one has to be a fool to do so. It is to instruct such fools that theologians formulate the proofs of the existence of God by showing them that it follows logically from things that they cannot deny.
As usual, St. Thomas begins by giving the arguments of those who deny the thesis he is going to prove; in this case, that the existence of God is not immediately obvious. The most important of these is the famous “ontological argument” of St. Anselm, who says that since God is the greatest thing that can be conceived of, it is obvious that He must exist, because it is greater to exist than not to exist.
In his response, St. Thomas concedes that, per se, it is true that God must exist because what He is includes existence, since, as we will see later, His very essence is existence, as He revealed to Moses: “I am Who am” (Ex. 3:14). Similarly, we know that if something is a man, then we know also that it is an animal, because animality belongs to the essence of man: in the same way, since existence belongs to the essence of God, He must exist.2
However, adds St. Thomas, even though all this is true in itself, for us it is not evident because we do not know what God is: we will only know that when we see His essence in the beatific vision. Furthermore, as we said, it must first be established that He exists before we can even begin speaking about what He is. Therefore we cannot argue from the fact that His essence includes existence to the fact that He actually exists. This is the fault in the argument of St. Anselm, for he starts with the idea of what God is and pretends to arrive, from there, to His actual existence. It is true that the idea of God includes His existence, so, if He exists, He must necessarily exist. But that doesn’t take us one step further to proving that He actually does exist, because this is still just an idea and not reality.
The importance of this little article today is obvious. A great many of our contemporaries, nursed from infancy on the myth of evolution, honestly think that God does not exist. St. Thomas shows us that they are not necessarily being hypocritical but are perhaps just confused, which should encourage us not to dismiss them as impious hooligans but rather help them to see that they are mistaken. It is true that theologians commonly teach that men cannot deny the existence of God without sinning but that does not necessarily mean that they are being positively deceitful: it may be that they simply are not making the necessary effort to use the reason God gave them in order to understand this truth.3
God’s existence can be proved by reason alone
1) Cardinal Ratzinger denies it
In a second article St. Thomas shows that, even though the existence of God is not immediately obvious, it can be demonstrated by reason. Here again this article is of great current interest since most people today—even many Catholics—believe that God’s existence is purely a question of personal faith and not of objective reason.4 By one of these strange paradoxes of which the modern world is so full, even though the new Catechism of the Catholic Church, edited by then Cardinal Ratzinger’s efforts, expressly repeats the traditional doctrine of Vatican I which declares that “God can be known with certainty from the created world by the light of natural reason,”5 he in a highly publicized conference he gave against relativism uttered the following words:
Certainly, the attempt to get out of the swamp of incertitude by means of a strictly autonomous reason, that doesn’t want anything to do with faith, cannot succeed. In fact, human reason is not at all autonomous. It always lives in particular historical contexts. Contingencies block its vision (as we have been able to ascertain). Thus it has need also to be helped on the historical level in order to be able to pass over the barriers that history puts in its path. I believe that neo-scholastic rationalism failed in its attempt to want to reconstruct the Preambula fidei 6 by a reason that is totally independent of the faith, by a purely rational certitude. All other attempts that follow the same route will obtain in the end the same results. Karl Barth was right on this point when he refuted philosophy as a foundation of the faith, independently from it: our faith would be founded, then, fundamentally, on changing philosophical theories.7
The only way to reconcile the Cardinal’s position with the teaching of Vatican I (quoted by his own catechism!) seems to be to say that although, per se, God can be known by reason alone, concretely in the world men live in after original sin, it is not possible in practice to arrive at this certainty without the help of faith. This interpretation of Vatican I, however, was ruled out by the spokesman of the commission who presented this text to the Council, who said explicitly: “The doctrine hereby submitted must be considered as universally true, whether man is viewed in the purely natural state or in that of fallen nature.”8
Garrigou-Lagrange comments on this saying:
Hence it cannot be maintained that, in consequence of original sin, there is no justification for the assertion that reason is assured of the objective validity of its conclusions, unless this same faculty is fortified by the superadded light of an illuminative grace.9
Nevertheless it seems that this must be the Cardinal’s position, and if we go back to his catechism we can see that it can be interpreted in this way as well, for after the clear restatement of the doctrine of Vatican I, it goes on immediately to talk about “history”:
In the historical conditions in which he finds himself, however, man experiences many difficulties in coming to know God by the light of reason alone.10
There is then a quote of Pius XII’s encyclical Humani Generis which speaks of the difficulty men can have in knowing God because of His transcendence and because of man’s weakness, especially after original sin, and the consequent need for revelation even of the truths about God which we can know by reason. This is all fine and dandy because this is perfectly Catholic doctrine (as the catechism shows by giving references to Vatican I and St. Thomas as well) but the fact remains that you cannot square Vatican I’s teaching about man’s real capability to know God by reason alone (even after original sin) and Cardinal Ratzinger’s rejection of it in his conference. Humani Generis, Vatican I and St. Thomas, in their remarks about the moral necessity of revelation so that men might know “easily, certainly and without error” the truth about God in no way imply that “a purely rational certitude” about God “independent of faith” is impossible as Cardinal Ratzinger says it is, for this would be to contradict what they say very clearly elsewhere. If Cardinal Ratzinger is capable of such contradictions because of his modern philosophy, the Church and St. Thomas certainly are not.11 When they speak of the moral necessity of revelation to confirm man’s knowledge about God, they in no way imply that by reason alone man cannot certainly know God. They simply mean that men, as a whole, have need of this revelation to hold firmly to all the truths they need to know about God in order to work out their salvation without being intimidated or confused by what their imagination or passions or false arguments might oppose to their natural certainty regarding these truths.
2) St. Thomas affirms it
St. Thomas quotes as an authority for his thesis that the existence of God can be proven by reason the text of St. Paul where he says: “The invisible things of Him are clearly seen, being understood by the things that are made” (Rm. 1:20).
But, he goes on, this would not be unless the existence of God could be demonstrated through the things that are made; for the first thing we must know of anything is, whether it exists.
He then explains that the sort of demonstration he is speaking of here is not like the demonstrations that prove a property of something by starting from its essence (as, for example, Euclid proves the properties of triangles by deducing them from the essence of what a triangle is12) but rather it simply proves that something exists starting from one of its effects.
From every effect, he says, the existence of its proper cause13 can be demonstrated, so long as its effects are better known to us. Since every effect depends upon its cause, if the effect exists, the cause must pre-exist. Hence the existence of God, in so far as it is not self-evident to us, can be demonstrated from those of His effects which are known to us.
We see, then, that this proof of the existence of God is something very humble. It contents itself with starting with things that belong to our own experience (“the things that are made” that we see around us) and concluding from them the existence of a cause that must exist to explain them.
By this humility St. Thomas ducks the objections that are made to the idea of proving God’s existence. “You can’t prove the existence of something that you don’t know the essence of,” says one objection, “and we’ll know God’s essence only when we see Him in heaven.” Response: “That is true in demonstrations that prove a property from the essence of something, as in geometry, but it isn’t necessary to know the essence of a thing in order just to prove it exists: all you have to do is have some idea about what the thing is (so that you know what you are talking about 14) and be able to prove that that particular thing you are talking about exists.”
Another objection attacks even this kind of argument: “But you can’t prove the existence of a cause from effects that aren’t proportionate to this cause, and God is a cause that is infinitely above all His effects, so there is no proportion.” Response: “It’s true that you cannot have a perfect knowledge of a cause by effects that aren’t proportionate to it, but you can at least know that it exists, and that is all we are trying to prove for the moment.”
A final objection reflects the position of Cardinal Ratzinger and says that we can’t prove that God exists because it is an article of faith. St. Thomas’s response provides a resounding refutation of the Cardinal’s opinion that the præambula fidei are impossible (and shows that they are not at all, as he pretends, something that comes from “Neo-scholastic rationalism”):
The existence of God and other like truths about God, which can be known by natural reason, are not articles of faith, but are preambles to the articles; for faith presupposes natural knowledge, even as grace presupposes nature, and perfection supposes something that can be perfected.
Nevertheless, there is nothing to prevent a man, who cannot grasp a proof, accepting, as a matter of faith, something which in itself is capable of being scientifically known and demonstrated.
This does not mean, as we said, that St. Thomas thinks that for some men the proof of the existence of God is impossible, but rather he just means that all men are not capable of understanding all the philosophical notions used in the scientific demonstrations of this truth and that, concretely, faith can help men to be firm in their certainty of it. Another passage of Garrigou-Lagrange is helpful here:
The question is not one of fact, as a note attached to the schema drawn up by the special commission [at Vatican I] on Catholic doctrine appropriately remarked: “The question is not whether, de facto, individual human beings derive their rudimentary knowledge of God from this natural manifestation, or if they are not rather urged to seek it in the revelation proposed to them, being made cognizant of His existence through the revealed teaching given to them. The point at issue is the power of reason.” The possibility defined is simply the physical possibility common to all human beings.15
1 Thus in his commentary on Aristotle’s work on logic, The Posterior Analytics, St. Thomas writes: “And just as when we know that this is such a thing, we ask why, so also when we know about something simply that it is, we ask what it is, for example, what is God, or what is man” (II Post. An., l. 1, n. 5). As John of St. Thomas remarks here, normally a science does not itself prove the existence of its own object, but since theology is a wisdom (that is, a science that treats of the highest, first causes) it reflects on its own principles and defends them and thus can defend the existence of its object, God the Author of the supernatural order, using the philosophical proofs of the existence of God the Author of nature.
2 John of St. Thomas explains this very clearly: “Existence is an essential predicate of God: for He is distinguished from created being in this that existence is not an essential predicate of creatures, but it is essential to God; for God is being that comes from itself (ens a se) and pure act, and consequently He exists by virtue of His specific reason (ex vi essentialis rationis suae).…It is impossible in the concept of pure act that existence be included only in potency.”
3 Cf. Rev. R. Garrigou-Lagrange, O.P., God: His Existence and His Nature, trans. Dom Rose (St. Louis: Herder, 1948), pp. 26-28. We can quote the following passage: “It has not been defined as de fide that there is no difficulty in the actual exercise of this natural power of reason (to prove the existence of God) but the doctrine itself is the commonly accepted teaching of theologians and is proxima fidei.…The reason for saying that this common teaching of theologians is proxima fidei is that Scripture declares pagans to be unreasonable and inexcusable for not having any knowledge of God (Rm 1:20-21; Wisd. 13:1-9).…All theologians deny the possibility of ignorance or of invincible error on the subject of God’s existence. This means that speculative atheism is an impossibility for any man who has the use of reason and is in good faith. Good faith, in the sense in which the Church understands the term, differs considerably from what the world generally means by it. It implies not only that sincerity which is contrary to deceit, but it also denotes that one has made use of all the means at his disposal in order to arrive at the truth. In the quest of truth one may fail deliberately, not only in a direct way, when one does not want to see the truth, but also in an indirect way, when one does not want to avail oneself of the means that one ought to use, or when through a perversion of the intellect, one agrees to doctrines that one ought to reject.”
4 This point of doctrine is not without relation to the question of religious liberty, for if religion is simply a matter of personal faith and cannot be judged by objective reason, then it becomes inconceivable that a public authority could intervene in religious matters since they would be a strictly personal affair, incapable of objective verification that can be recognized by everyone. Thus it is not a coincidence that the neo-modernists who deny the rational proofs of the existence of God and of the truth of the Catholic faith also preach religious liberty.
5 Catechism of the Catholic Church, No. 36, which cites here Vatican I, Dei Filius 2, DS 3004.
6 “The preambles of the faith,” that is, the fundamental truths necessary as a preparation for the act of faith, of which the most important is the existence of God. The Cardinal does not seem troubled by the contradiction involved in the idea of these preambles to the faith depending on faith itself.
7 Documentation Catholique, No. 1 “hors série,” 2005, p. 55, which reproduces a conference at Guadalajara in May 1996; Documentation Catholique, No. 2151, 1997, pp. 29-37.
8 Vacant, Études sur le Concile du Vatican, I, 29, 673, quoted by Garrigou-Lagrange, op. cit., p. 27.
9 Op. cit., p. 27.
10 No. 37.
11 If indeed the Cardinal’s position is the proper interpretation of the Catechism, it shows how wary we must be when we hear modern churchmen quoting traditional doctrine. As for the remarks about Karl Barth (a Protestant “theologian”), they reveal a surprising ignorance of the simplest elements of traditional apologetics. The Præambula fidei are a foundation of the rational credibility of the faith, not of faith itself, which is founded on the authority of God who reveals Himself to us.
12 This is the type of demonstration that St. Anselm uses but which, as we saw, cannot be used to prove God’s existence because we cannot know what God is here below and so we can’t deduce anything about Him from His essence. Also, such an argument based on the essence of something cannot prove anything about its existence, which much be established first from some other source.
13 “The proper cause is that which can produce a certain effect by itself (per se) and immediately as such (primo).…Thus to carve a statue requires a sculptor. To say it requires an artist would be to designate too general a cause.…Similarly, it would not be definite enough to say that the movements in the universe require a primary being: what they immediately demand is a prime mover.” Garrigou-Lagrange, op. cit., p. 379.
14 This is what is called the “nominal definition” of something, that is, what is meant by its name. Thus the five proofs St. Thomas gives all end with the words: “And this (that is this cause that we have proven must exist) is what all call God.”
15 Op. cit., p. 27. The whole first chapter of Garrigou-Lagrange’s God: His Existence and His Nature provide a clear exposition of the magisterium’s teaching on this point and show that the neo-modernist position was explicitly condemned in advance.
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