Also known as the Angelic Doctor (1225-1274). Born and died in Naples, Italy, although he traveled a lot. One of the most important intellectuals of western culture. He wrote the Summa Theologica, an enormous piece of theology and logic philosophy, in which he exposed his Five Ways to prove the existence of God.

Whether God Exists
From Summa Theologica, Part I

Objection 1: It seems that God does not exist: because if one of two contraries be infinite, the other would be altogether destroyed. But the word "God" means that He is infinite goodness. If, therefore, God existed, there would be no evil discoverable; but there is evil in the world. Therefore, God does not exist.

Objection 2. Further, it is superfluous to suppose that what can be accounted for by a few principles has been produced by many. But it seems that everything we see in the world can be accounted for by other principles, supposing God did not exist. For all natural things can be reduced to one principle, which is nature; and all voluntary things can be reduced to one principle, which is human reason, or will. Therefore, there is no need to suppose God's existence.

On the contrary, It is said in the person of God: I am Who am (Exod. iii. 14)

I answer that, The existence of God can be proved in five ways.

The first and more manifest way is the argument from motion. It is certain, and evident to out senses, that in the world some things are in motion. Now whatever is in motion is put in motion by another, for nothing can be in motion except it is in potentiality to that towards which it is in motion; whereas a thing moves inasmuch as it is in act. For motion is nothing else than the reduction of something from potentiality to actuality, except by something in a state of actuality. Thus that which is actually hot, as fire, makes wood, which is potentially hot, to be actually hot, and thereby moves and changes it. Now it should be at once in actuality and potentiality in the same respect, but only in different respects. For what is actually hot cannot simultaneously be potentially hot; but it is simultaneously potentially cold. It is therefore impossible that in the same respect and in the same way a thing should be both mover and moved, i.e., that it should move itself. Therefore, whatever is in motion must be put in motion by another. If that by which it is put in motino be itself put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeign that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand. Therefore, it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.

The second way is from the nature of the efficient cause. In the world of sense we find there is an order of efficient causes. There is no case known (neither is it, indeed, possible) in whcih a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible. No in efficient causes it is not possible to go on to infinity, because in all efficient causes following in order, the first is the cause of the intermediate cause, and the intermediate cause is the cause of the ultimate cause, whether the intermediate cause be several, or one only. Now to take away the cause is to take away the effect. Therefore, if there be no first cause among efficient causes, there will be no ultimate, nor any intermediate cause. But if in efficient causes it is possible to go on to infinity, there will be no first efficient cause, neither will there be an ultimate effect, not any intermediate efficient causes, all of which is plainly false. Therefore, it is necessary to admit a first efficient cause, to which everyone gives the name of God.

The third way is taken from possibility and necessity, and runs thus. We find in nature things that are possible to be and not to be, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be. But it is impossible for these always to exist, for that which is possible not to be at some time is not. Therefore, if everything is possible not to be, then at one time there could have been nothing in existence. Now if this were true, even now there would be nothing in existence, because that which does not exist only begins to exist by something already existing. Therefore, if at one time nothing was in existence, it would have veen impossible for anything to have begun to exist; and thus even now nothing could be in existence-- which is absurd. Therefore, not all beings are merely possible, but there must exist something the existence of which is necessary. But every necessary thing either has its necessity caused by another, or not. Now it is impossible to go on to infinity in necessary things which have their necessity caused by another, as hasalready been proven in regard to efficient causes. Therefore, we cannot but postulate the existence of some being having of itself its own necessity, and not receiving if from another, but rather causing in others their necessity. This all men speak of as God.

The fourth way is taken from the gradation to be found in things. Among beings there are some more and some less good, true, noble, and the like. But "more" and "less" are predicted of different things, according as they resemble in their different ways something which is the maximum, as a thing is said to be hotter according as it more neary resembles the hottest; so that there is something which is truest, something best, something noblest, and, consequently, something which is the uttermost being; for those things that are greatest in truth are greatest in being. Now the maximum in any genus is the cause of all in that genus; as fire, whcih is the maximum of head, is the cause of all hot things. Therefore, there must also be something which is to all beings the cause of their being, goodness, and every other perfectino; and this we call God.

The fifth way is taken from the governance of the world. We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly, do they achieve their end. Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore, some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

Reply to Objection 1. As Augustine says: SInce God is the highest good, He would not allow any evil to exist in His works, unless His omnipotence and goodness were such as to being good even out of evil. This is part of the infnite goodness of God, that He should allow evil to exist, and out of it produce good.

Reply to Objection 2. Since nature works for a determinate end under the direction of a higher agent, whatever is done by nature must needs be traced back to God, as to its first cause. So, also, whatever is done voluntarily must also be traced back to some higher cause other than human reason or will, since these can change and fail; for all things that are changeable and capable of defect must be traced back to an immovable and self-necessary first principle, as was shown in the body of the Article.

Saint Thomas Aquinas (1225-1274)

Philosopher, theologian, doctor of the Church (Angelicus Doctor), patron of Catholic universities, colleges, and schools. Born at Rocca Secca in the Kingdom of Naples, 1225 or 1227; died at Fossa Nuova, 7 March, 1274.

St. Thomas Aquinas was known as the "Dumb Ox" as a child, because he was rather large (there is a legend, probably apocryphal, that claims that they had to carve a half moon out of the dining table in order to let him sit down), and completely silent in for one occasion, when he blurted out "What is God?" His fellow students mistook him for a dunce, but St. Thomas soon began to show signs of remarkable intelligence and insight, exceeding even the abilities of his teachers (later in life, St. Thomas said "I thank God that I have understood every word that I have read," or something to that effect). Against his parent's wishes (he was born into a rich family, and they wanted him to become a comfortable abbot of a reputable monastary), he joined the Dominicans, which was an order of wandering friars, and required a vow of holy poverty. His family, irate beyond belief, imprisoned him and attempted to bodily restrain him from fulfilling his vocation. Eventually, they relented, as St. Thomas combined perfect humility with incredible stubborness when it came to his beliefs.

St. Thomas studied under Albertus Magnus, and eventually obtained a doctorate of Theology at the University of Paris. He applied his incredible intellectual gifts to the end of explaining and defending the Christian faith, and was the first Catholic theologian to explain the philosophy of Aristotle, and to use Aristotle both to deepen our understanding of the Catholic Faith, and to explain the compatibility of Faith and Reason. St. Thomas Aquinas wrote countless treatises, prayers, and philosophic commentaries, and is most famous for the Summa Theologica, which he modestly called a manual of Christian doctrine. His writings are among the most influential in history, and are a landmark in theology and philosophy. For these reasons, as well as his piety, holiness, prayerful life, and obedience to the will of God, St. Thomas Aquinas was canonized in 1323 by Pope John XXII, and proclaimed a doctor of the Church by Pope Pius V in 1567. G.K. Chesterton has written an excellent and entertaining biography of St. Thomas, titled "The Dumb Ox", and published by Ignatius Press.

Perhaps Thomas Aquinas' greatest historical contribution to theology was his attempt to reconcile reason and theological dogma, to find authenticity and value in reason within the Christian faith.

Aquinas was born into great wealth (and probably the aristocracy), but refused to take on the life of ease which he would have enjoyed, his scholastic aptitude and inquisitive intellect taking precedence having matured through his early years of education at the monastery of Monte Cassino under the tutelage of his uncle, the abbott. His family actually seized and confined him for a year, at the age of nineteen, hoping to dissuade him from his intellectual preoccupations, urging him to taking up a respectable life fitting his social position. He escaped to Paris and the tutelage of Albertus Magnus, who also guided his later departure to Cologne. Magnus greatly shaped the views which he would later systematize, though Aquinas disagreed in many ways with some of his teacher's ideas.

Thomas Aquinas as Philosopher and Theologian

Aquinas made extensive use of Aristotelian philosophy, eventually producing a synthesis with Christian theological dogma through its aid. Unlike Augustine and many other founders of the Christian faith, he rejected Neoplatonic metaphysics and Plato's idea of a reality of pure forms and eternal ideas. We would consider his essentially Aristotelian view almost pre-scientific: he believed in the reality of acquiring knowledge through the data that the senses perceive, rather than a more dualistic conception which held matter as somehow fallen and evil.

This isn't to say that he believed in the reality of the world of the senses -- quite the contrary. But he maintained that the data of the senses cannot be in fundamental conflict with faith or reason. He held that reason and - through it - knowledge, were authentic modes of revelation and connection to God. Even if (for Aquinas) faith must be placed above them, it was for him a faith of suprarational, transcendent status. Aquinas believed that the Will of God, not his Reason nor Mind, had initiated the creation. God thus was the sustainer of the created beings, and had originally created that-which-is from that-which-is-not.

The idea that the reality of God required a denial of reason would have been abhorrent to him. He in fact rejected these theological ideas, among others:

  • the self-evidence of God,
  • that God was incomprehensible to man,
  • that humans were incapable of recognizing the qualities of God
  • Jesus Christ as the necessary occurence, not a choice by God, for the salvation of the human race.
    (For Aquinas, implying such a necessity would remove the absolute freedom which belonged to deity. Thus the manifestation of Christ was a method of salvation freely chosen by God, not an obligation or requirement.)

He believed that the attributes of God could be known by man through the combination of reason and faith. To Aquinas, nature and reason were dual modes of divine revelation necessary and complementary to proper faith.

The nature of the creature was to be ascertained through the data of the senses and reason. But he asserts that man has a spiritual and supernatural aspect as well, which alone is capable of that contemplation in which the spiritual man's happiness rests and to which man, in this life, could never attain in fullness, and which was beyond his unaided intellect. It was the province of faith, but faith did not bring it about any more than intellect - it could occur only as an outpouring of divine goodness, through an act of the Divine Will.

This bestowal of grace could be effected through the sacraments, which themselves derived their power from the passion of Christ. It resulted in a "new birth" by the creative act of God.


Needless to say, Aquinas upset many of the popular theological dogmas prevalent before him. His Summa Theologiae remained unfinished by the time of his death, but his ideas passed into the official theology of the church, providing Christianity with a genuine intellectual foundation. Aquinas' work strongly influenced the philosophical climate of Western Europe and gave reason a legitimate place in Christian theology.

  • Latourette, Stephen. A History of Christianity, Volume I: Beginnings to 1500. Harper-Collins, 1956,1975, pp. 509-514
This is an essay I wrote for my philosophy class.

On Saint Thomas Aquinas's proofs for the existence of God

Among the philosophers of the Middle-Ages there arose the branch of philosophy known as Scholasticism, which attempted to reconcile the Aristotelian world view with Christian dogma. One of the more curious aspects of this movement was the attempt to prove the existence of God by rational means. I call this curious because religion is often thought of as something decidedly irrational, indeed, one of the Church Fathers is said to have stated "Credo quia absurdum est." Even so, the proofs for the existence of the Deity put forth by the most famous and influential of the scholastics, Saint Thomas Aquinas (1225-1274), are included in the official doctrines of the Catholic Church to this day.

One of Thomas's most important proofs is premised on the idea that all movement has a cause. For a body to move, there must be something to cause the movement. As it is clear that there is an abundance of movement in the world, according to Saint Thomas it is clear that some being must have initiated the first movement. It follows that because God is this First Mover, God exists.

The most common critique of this line of argument is that if all movement must be caused by some being, it follows that even God would have to have a mover in order to move. This implies an infinite series of movers. This type of critique is fully justified, even though Saint Thomas himself rejected it as irrational. Even though our Western mode of thought seduces us to believe that a definite beginning and end exist, that there is an alpha and an omega, I think that in this particular case it is more sensible to think that movement has always existed, and that there is thus no need for a First Mover.

It should be pointed out that even if we accept Saint Thomas's theory about the First Mover, this does not necessarily mean that the Mover is the Christian God. It can be any being capable of movement, even totally different from Thomas's God. By no means does this being need to be omnipotent - the only one of its abilities which can be inferred from Thomas's argument is that it is capable of initiating movement, which isn't very much. If we take the matter a bit further, it becomes apparent that the whole being is unnecessary. Only the event, the movement, is what is needed. This is because the being initiating the first movement is not essential, the movement itself is. To this Saint Thomas would of course say that this first movement would need someone to cause it, but then we could return to our first objection to his theory that even the First Mover needs a mover.

A rather more interesting argument Saint Thomas presents is based on a conception of possibility derived from Aristotle, which was popular among medieval philosophers. Saint Thomas, along with Aristotle, thought that every single possible event occurs at some point in time, or in other words, if an event is possible, it is so in virtue of happening. Therefore, the universe in a way goes through every possible state of affairs from the beginning of time to the end thereof. As all existing things could according to Saint Thomas also not exist, there was once a time when nothing existed. If such a point in time did indeed exist, then it would follow that nothing could be created either, as nothingness cannot become anything by itself. It is however evident, that at least some things exist at the present moment, which means that even in the time when presumably nothing existed, something had to exist in order to create something out of the nothingness. Therefore God had to exist even when nothing else existed to create everything in existence now.

This argument can be criticized by pointing out that the theory of possibilities on which it is based is rather odd, and quite alien to the modern philosopher. This is because it is not logically contradictory to say that some event is possible, even though it never happens. It is possible for me to rise up from my chair right now - sitting and writing instead does not change this. Even if I never rose up from my chair this would not mean that rising from the chair is impossible. The same holds the other way round - if something has happened, it does not mean that it might not have been possible that the event in question had not happened. We cannot change the past, but that does not mean that the past had to unfold the way it did. Even though Bertrand Russell won the Nobel Prize in literature, this does not mean that he had to. It is no use denying Russell's win today, but it does not follow that he was the only possible winner. Russell's win of the prize is not implied in the definition of the Nobel Prize, nor is it an essential part of Russell's definition, as it is nonsensical to assert that Russell would not be Russell had he not won the prize. Of course, there is a very great risk of committing an anachronism here, as the concept of possibility is very much dependent on perspective, and ours differs to a great degree from the medieval one. Perhaps Saint Thomas would view our notion of possibility as at least as odd as we view his. Therefore it is necessary to note that even if we accepted his view of possibility, our critique of the first mover would be valid here also.

Saint Thomas is not content to stop here, however. His next argument is based on the supposition that values and valuations must have an absolute basis. Because we say that something is good or bad, some person noble and wise, these terms must be based on something real. A being that is absolutely noble, wise, and so forth must exist for us to speak of gradations of rank in these characteristics. In other words, if we are to say that A is more noble than B, we have to compare A and B to an 'absolute nobility'. A is more noble than B because A is more similar to the 'absolute nobility' than B.

This is quite a Platonic line of reasoning. Less than perfect things, in other words everything existing in this world, are shadows of something perfect, which is beyond this world. To Plato, these perfections are Ideas, to Saint Thomas, they are a part of God.

I think Saint Thomas is wrong in thinking that we compare an adjective to some maximal manifestation of the adjective. To use an example of his, I think it is possible to say that an object is hot without comparison with an 'absolute hotness'. It is not even necessary to know what the 'absolute hotness' might be; we only need to know that some other object is less warm than the object we call 'hot'.

At the basis of the Platonic theory of Ideas and Thomas's proof is another assumption which I hold to be incorrect. They both take it for granted that our adjectives refer to something in the actual world. However, the word 'noble', for example, is a thoroughly human invention, and would be altogether meaningless outside human society. It is also possible to have different, but still justifiable, definitions of 'noble', which means that the word has no objective basis. This holds for all other adjectives as well, therefore we must reject this proof for the existence of God, too.

The last of Saint Thomas's proofs I am going to discuss is the most interesting and convincing. It is again based on an Aristotelian notion, that of the purposefulness of nature. Aristotle pointed out that animals behave in very sensible ways even though their intelligence can be assumed to be rather limited. For example, several species of birds fly south to escape the cold of winter. They clearly do not have the capacity to reason that this would be a sensible course of action, so how is it possible that in spite of this they behave in this very wise fashion?

The answer Saint Thomas Aquinas gives to this problem is that God makes the birds fly to the south, and all other animals to behave in sensible, life-preserving ways. Before Darwin, this was a very convincing argument. The probability that the animals would act this way by chance is too low. Because of this, biologist Richard Dawkins asserts in his book The Blind Watchmaker that atheism was not a serious philosophical stance before the theory of natural selection, and he is probably right. Darwin has shown, however, that the methods of natural science are sufficient to explicate the seemingly sensible behaviour of animals. Saint Thomas's last argument is therefore also incorrect, but we should not criticize him for it too harshly, because he did not have the scientific knowledge required to understand this question.

Aquinas, Saint Thomas. Summa Theologica.
Russell, Bertrand. A History of Western Philosophy.
Saarinen, Esa. Länsimaisen filosofian historia huipulta huipulle Sokrateesta Marxiin.

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