- The Summa Theologica by Thomas Aquinas


Between 70 B.C. and 390 A.D. the preservation and transmission of the Greco-Roman culture were ensured. The Greeks had an intellectual tradition and the Romans offered a stable empire where it could develop. However, the Roman empire began to crumble in the fourth century because of internal conflict and the border harassment of its legions: the countrymen of Gaul rebelled, there were massive migrations of Goths (369), Christian insurgents in Alexandria (391 ), Visigoth, Arab and Hun invasions that occupied the empire's territories, class conflicts between pagans and Roman Christians and economic mismanagement due to the over taxation of the merchant class, among other factors. The stability of the empire fell into chaos and with economic restrictions libraries and the traditional preservation of culture also suffered.

Despite the fact that after 750 there was a civil war within the Arab empire, then led by the Omeya dynasty, its power in the Iberian peninsula remained stable with the capital in Cordoba becoming a world centre of knowledge. In spite of the incipient Christian reconquest and the first crusade initiated by Pope Urban II in 1095, there was an intensification of the exchange of knowledge between the Andalusian centres and the rest of Europe. By the year 1275 Christianized Arab merchants had established the first paper mills in Spain. 50 years later the University of Paris employed 10,000 copyists. Even during the Inquisition the exchange of knowledge continued from south to north and the humanistic spirit of the Renaissance was able to expand thanks to the ideas found in Iberia's Arabian books.

The intellectual exchanges were made possible by scholarly pilgrims who travelled to Muslim Hispania to learn about and translate the documentary information that the Arabs stored in their libraries. The work of pilgrim researchers was to harmonize ancient knowledge with the Christian faith. Between 1150 and 1250 all of Aristotle's writings were translated and introduced to the West along with Arabic commentaries by Avicenna and Averroes.

Thomas Aquinas (1225 - 1274) took up the main challenge of medieval philosophy which was the reconciliation between faith (theology) and philosophy (reason). A way had to be found to link the knowledge gained from biblical revelation and the information observed using the mind and senses.

Averroes had proposed the theory of double truth arguing that the two types of knowledge were possible but opposed. Aquino's revolutionary vision rejected this approach, proposing that both types of knowledge were compatible because they came from God. Beyond compatibility, he claimed that they could collaborate because revelation could guide reason and prevent errors while reason could clarify and demystify faith. Within this double conception Aquinas proposed that the existence of God could be proved using five rational arguments.

Among his almost 60 written works The Summa Theologica stands out, composed between 1265 and 1274. It is a huge effort to unite the thought of Aristotelian natural philosophy and Christian theology. His next work Summa Contra Gentiles is an apologetics of Christian beliefs in the medieval tradition of proselytizing.

Aquinas moved intellectual attention from the traditional ecclesiastical focus on Plato to interest in Aristotle. Plato considered that the proper object of study was the Forms as they were the only reality. Augustine of Hippo in the fourth century saw Plato's division of two worlds (the perfect versus the imperfect) as an excellent mirror of the Christian earthly / divine duality. 

Drawing from Jewish and Islamic texts on Aristoteles Aquinas assimilated his pholosophy into a new approach to Christian thinking which became official Church doctrine.


The main goal of the Summa was a summary of all theology known at the time. It was unfinished at his death. The central line of the treatise is that reason and revelation are complementary. The process Aquinas followed was the reconciliation of Christian thought with ideas of Aristotle whose work was being rediscovered by Europeans at that time through Islamic and Jewish texts.  He cites Aristotelian sources as well as Arab philosophers like Averroes and the Jewish rabbi Maimonides. Aquinas' aim is to offer a truly universal and rational view of all existence.

The Summa is divided into three sections :

- Part 1 deals with theology : God and the Creation from the angels to humans. The discussions cover 119 questions also dealing with the nature of God, the essence and nature of humanity and divine government.

- Part 2 concerns ethics and addresses humanity. It deals with 303 questions on habits, purpose, law, vices and virtues, the religious and the secular life.

- Part 3 is about Jesus Christ as mediator between God and humanity. There are 90 questions dealing with the Incarnation, the Sacraments and the Resurrection.

- There is a supplement which includes 99 more questions on various topics such as excommunication, indulgences, confession, marriage, purgatory, the saints and the damned.

The process for discussions follows scholastic methodology. This is a set pattern named Disputatio : the presentation of the case against a position then the refutation of that case point by point while offering your own interpretation, the Determinatio, citing relevant authorities.

The Disputatio process of arguing his case assumes that Aquinas is not only a philosopher pursuing truth but above all an ecclesiastic working to save humanity through a rationalisation of divine revelation. Belief is fundamental to his approach. He thus applies reason to examine the existence of God, the limits of human knowledge and the purpose of humanity. Aristotle is used not as a critical tool to examine Church beliefs but as a way of rationally underpinning beliefs already held. 


Aristotle’s Four Causes

Aquinas uses Aristotle's Four Causes as the framework for this treatise. The Four Causes are:

- The material cause which concerns the material world. Matter is potentiality, that is, becoming. Aquinas uses this cause in analysing human knowledge and also in the proofs of God's existence.

- The formal cause is the pattern into which a thing fits, its essence. The author uses this in the theory of knowledge and the conception of God who is the only pure formal cause. 

- The efficient cause indicates that an effect will follow. Aquinas uses this concept in the theory of knowledge about the physical world and human actions which are directed by the will

- The final cause is the purpose of something. This explains the nature of the will which seeks to contemplate the Divine Essence.

Existence and Essence

Aquinas revolutionised Christian tradition by favouring Aristotle over Plato. Plato maintained that ultimate reality was essence whereas Aristotle argued that existence came first. Plato rejected sensory experience as a source of knowledge and so true knowledge is only found in general ideas, their essence. Existence for Platonists is the everyday world of single items such as cats, dogs, tables and chairs. These are inferior to essences. Augustine of Hippo applied Plato's idealism to the Christian division of corrupt matter and heavenly spirits.

Aquinas criticises Plato's theory because it cannot explain the origin of existence. He argues that the scriptures saw the Creation as good and Moses' definition of God as "I am that I am", in other words a Being itself. For Aquinas the end purpose of humanity was developing towards Being. Previous to Aquinas Church teaching taught that existence was the obstacle to our spiritual destiny. He argued that this destiny consisted in enhancing our existence.

The existence of God

The existence of God is dealt with in three articles following the process of Disputatio >

Article 1 proposes that the statement "God exists" is self-evident but humans need a demonstration.

Article 2 concludes that a demonstration is possible despite arguments against it.

Article 3 offers Five Ways to prove God exists.

Article 3. Whether God exists?

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." (Exodus 3:14)

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 our 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. But nothing can be reduced 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 is not possible that the same thing 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 motion be itself put in motion, then this also must needs be 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; seeing 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 which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible. Now 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 is the cause of the ultimate cause, whether the intermediate cause be several, or only one. 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, nor 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 been impossible for anything to have begun to exist; and thus even now nothing would 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 has been already proved in regard to efficient causes. Therefore we cannot but postulate the existence of some being having of itself its own necessity, and not receiving it 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 predicated 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 nearly resembles that which is hottest; so that there is something which is truest, something best, something noblest and, consequently, something which is uttermost being; for those things that are greatest in truth are greatest in being, as it is written in Metaph. ii. Now the maximum in any genus is the cause of all in that genus; as fire, which is the maximum heat, 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 perfection; 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 (Enchiridion xi): "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 bring good even out of evil." This is part of the infinite 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 or 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.

Summary >

1. Things are in motion in the world and if we think back we will conclude that there is an unmoved first mover who is God.

2. Everything has a cause and nothing causes itself. The first cause in this chain of events is what we term God.

3. In Nature things exist then cease to exist. Everything that exists needs something that already existed for its existence. This necessary existence is what people call God.

4. There are characteristics which we can observe like good, true, noble and so on. There must be a maximum of each of these which causes them. This maximum is God.

5. All observable objects tend towards the best purpose though they are unaware of it. The guide of this plan must possess knowledge and intelligence like the arrow in the archer's bow. This intelligence is God.

Human Knowledge

Aquinas thinks of knowledge as part of the soul's capabilities because the intellect is a part of the soul. Reason is the essence of humanity though rationality is not their complete essence. 

Real knowledge for Aquinas is universal but not Plato's knowledge of ideas in the mind. He believes that if all knowledge were mental then there would be no use for the body. Following Aristotle he includes the senses in the act of knowing and insists against Plato that our mental images (phantasms) derive from the senses. Sensory experience is the passive part of knowledge and the mind is the active part which constructs ideas of universals.

It is through abstraction that we grasp the essence of material things. Mental images are universal concepts and particular material objects are unknowable precisely because we have images of them in the mind. All knowledge is abstract and that makes possible scientific knowledge of cause and effect. However, we are limited in our knowledge through abstractions. Infinity is a knowable concept because we can add numbers infinitely but we cannot comprehend an infinite series of numbers.


"Article 1. Whether man can attain happiness?

Objection 1. It would seem that man cannot attain happiness. For just as the rational is above the sensible nature, so the intellectual is above the rational, as Dionysius declares (Div. Nom. iv, vi, vii) in several passages. But irrational animals that have the sensitive nature only, cannot attain the end of the rational nature. Therefore neither can man, who is of rational nature, attain the end of the intellectual nature, which is Happiness.

Objection 2. Further, True Happiness consists in seeing God, Who is pure Truth. But from his very nature, man considers truth in material things: wherefore "he understands the intelligible species in the phantasm" (De Anima iii, 7). Therefore he cannot attain Happiness.

Objection 3. Further, Happiness consists in attaining the Sovereign Good. But we cannot arrive at the top without surmounting the middle. Since, therefore, the angelic nature through which man cannot mount is midway between God and human nature; it seems that he cannot attain Happiness.

On the contrary, It is written (Psalm 93:12): "Blessed is the man whom Thou shalt instruct, O Lord."

I answer that, Happiness is the attainment of the Perfect Good. Whoever, therefore, is capable of the Perfect Good can attain Happiness. Now, that man is capable of the Perfect Good, is proved both because his intellect can apprehend the universal and perfect good, and because his will can desire it. And therefore man can attain Happiness. This can be proved again from the fact that man is capable of seeing God, as stated in I, 12, 1: in which vision, as we stated above (I-II:3:8) man's perfect Happiness consists.

Reply to Objection 1. The rational exceeds the sensitive nature, otherwise than the intellectual surpasses the rational. For the rational exceeds the sensitive nature in respect of the object of its knowledge: since the senses have no knowledge whatever of the universal, whereas the reason has knowledge thereof. But the intellectual surpasses the rational nature, as to the mode of knowing the same intelligible truth: for the intellectual nature grasps forthwith the truth which the rational nature reaches by the inquiry of reason, as was made clear in I:58:3; I:79:8. Therefore reason arrives by a kind of movement at that which the intellect grasps. Consequently the rational nature can attain Happiness, which is the perfection of the intellectual nature: but otherwise than the angels. Because the angels attained it forthwith after the beginning of their creation: whereas man attains if after a time. But the sensitive nature can nowise attain this end.

Reply to Objection 2. To man in the present state of life the natural way of knowing intelligible truth is by means of phantasms. But after this state of life, he has another natural way, as was stated in I:84:7; I:89:1.

Reply to Objection 3. Man cannot surmount the angels in the degree of nature so as to be above them naturally. But he can surmount them by an operation of the intellect, by understanding that there is above the angels something that makes men happy; and when he has attained it, he will be perfectly happy."

Unhappiness comes from desire because the intellect searches for the essence. The end purpose of humanity is happiness and this cannot be found in any material thing but only in God, the source of all good. This involves the contemplation of the divine essence in the afterlife. 

Happiness excludes evil and since there is evil in this world so complete happiness here is impossible. Final happiness is the reward for a virtuous life.

Aquinas applies Aristotelian ideas of final cause since the human will is an efficient cause and happiness, contemplation of the Divine Essence, is the final cause. The will motivates humans to seek happiness but it is only by performing the will of God through works of virtue that we can reach final happiness.

The rest of the Summa is dedicated to examining these works of virtue and sin as well as explaining the role of Christ as mediator between God and humanity.

Philosophy and Theology

The primary purpose of the Summa is theological, that is, based on faith. Philosophy is used to prop up the theological concepts with rational arguments. For Aquinas theology has been revealed by God and philosophy, according to Aristotle, is knowledge gained through sensory experience and reason. This implies that philosophy cannot fathom some theological concepts such as the Trinity. Philosophy is thus a subset of theology - all theologians are philosopher while all philosophers are not theologians. Complete knowledge cannot come from philosophy, only from theology.

No comments:

Post a Comment