Thomas Aquinas (b. 1225 or 1226, d. 1274) is regarded as the greatest of scholastic philosophers. In all Catholic educational institutions that teach philosophy his system has to be taught as the only right one; this has been the rule since a rescript of 1879 by Leo XIII. St Thomas, therefore, is not only of historical interest, but is a living influence, like Plato, Aristotle, Kant, and Hegel—more, in fact, than the latter two. In most respects, he follows Aristotle so closely that the Stagyrite has, among Catholics, almost the authority of one of the Fathers; to criticize him in matters of pure philosophy has come to be thought almost impious.1 This was not always the case. In the time of Aquinas, the battle for Aristotle, as against Plato, still had to be fought. The influence of Aquinas secured the victory until the Renaissance; then Plato, who became better known than in the Middle Ages, again acquired supremacy in the opinion of most philosophers. In the seventeenth century, it was possible to be orthodox and a Cartesian; Malebranche, though a priest, was never censured. But in our day such freedoms are a thing of the past; Catholic ecclesiastics must accept St Thomas if they concern themselves with philosophy.

St Thomas was the son of the Count of Aquino, whose castle, in the kingdom of Naples, was close to Monte Cassino, where the education of the 'angelic doctor' began. He was for six years at Frederick II's university of Naples; then he became a Dominican and went to Cologne, to study under Albertus Magnus, who was the leading Aristotelian among the philosophers of the time. After a period in Cologne and Paris, he returned to Italy in 1259, where he spent the rest of his life except for the three years 1269–72. During these three years he was in Paris, where the Dominicans, on account of their

Aristotelianism, were in trouble with the university authorities, and were suspected of heretical sympathy with the Averroists, who had a powerful party in the university. The Averroists held, on the basis of their interpretation of Aristotle, that the soul, in so far as it is individual, is not immortal; immortality belongs only to the intellect, which is impersonal, and identical in different intellectual beings. When it was forcibly brought to their notice that this doctrine is contrary to the Catholic faith, they took refuge in the subterfuge of 'double truth'; one sort, based on reason, in philosophy, and another, based on revelation, in theology. All this brought Aristotle into bad odour, and St Thomas, in Paris, was concerned to undo the harm done by too close adherence to Arabian doctrines. In this he was singularly successful.

Aquinas, unlike his predecessors, had a really competent knowledge of Aristotle. His friend William of Moerbeke provided him with translations from the Greek, and he himself wrote commentaries. Until his time, men's notions of Aristotle had been obscured by Neoplatonic accretions. He, however, followed the genuine Aristotle, and disliked Platonism, even as it appears in St Augustine. He succeeded in persuading the Church that Aristotle's system was to be preferred to Plato's as the basis of Christian philosophy, and that Mohammedans and Christian Averroists had misinterpreted Aristotle. For my part, I should say that the De Anima leads much more naturally to the view of Averroes than to that of Aquinas; however, the Church, since St Thomas, has thought otherwise. I should say, further, that Aristotle's views on most questions of logic and philosophy were not final, and have since been proved to be largely erroneous; this opinion, also, is not allowed to be professed by any Catholic philosopher or teacher of philosophy.

St Thomas's most important work, the Summa contra Gentiles, was written during the years 1259–64. It is concerned to establish the truth of the Christian religion by arguments addressed to a reader supposed to be not already a Christian; one gathers that the imaginary reader is usually thought of as a man versed in the philosophy of the Arabs. He wrote another book, Summa Theologiae, of almost equal importance, but of somewhat less interest to us because less designed to use arguments not assuming in advance the truth of Christianity.

What follows is an abstract of the Summa contra Gentiles.

Let us first consider what is meant by 'wisdom'. A man may be wise in some particular pursuit, such as making houses; this implies that he knows the means to some particular end. But all particular ends are subordinate to the end of the universe, and wisdom per se is concerned with the end of the universe. Now the end of the universe is the good of the intellect, i.e. truth. The pursuit of wisdom in this sense is the most perfect, sublime, profitable, and delightful of pursuits. All this is proved by appeal to the authority of the 'The Philosopher', i.e. Aristotle.

My purpose (he says) is to declare the truth which the Catholic Faith professes. But here I must have recourse to natural reason, since the gentiles do not accept the authority of Scripture. Natural reason, however, is deficient in the things of God; it can prove some parts of the faith, but not others. It can prove the existence of God and the immortality of the soul, but not the Trinity, the Incarnation, or the Last Judgment. Whatever is demonstrable is, so far as it goes, in accordance with the Christian faith, and nothing in revelation is contrary to reason. But it is important to separate the parts of the faith which can be proved by reason from those which cannot. Accordingly, of the four books into which the Summa is divided, the first three make no appeal to revelation, except to show that it is in accordance with conclusions reached by reason; only in the fourth book are matters treated which cannot be known apart from revelation.

The first step is to prove the existence of God. Some think this unnecessary, since the existence of God (they say) is self-evident. If we knew God's essence, this would be true, since (as is proved later) in God, essence and existence are one. But we do not know His essence, except very imperfectly. Wise men know more of His essence than do the ignorant, and angels know more than either; but no creature knows enough of it to be able to deduce God's existence from His essence. On this ground, the ontological argument is rejected.

It is important to remember that religious truths which can be proved can also be known by faith. The proofs are difficult, and can only be understood by the learned; but faith is necessary also to the ignorant, to the young, and to those who, from practical preoccupations, have not the leisure to learn philosophy. For them, revelation suffices.

Some say that God is only knowable by faith. They argue that, if the principles of demonstration became known to us through experience derived from the senses, as is said in the Posterior Analytics, whatever transcends sense cannot be proved. This, however, is false; and even if it were true, God could be known from His sensible effects.

The existence of God is proved, as in Aristotle, by the argument of the unmoved mover.2 There are things which are only moved, and other things which both move and are moved. Whatever is moved is moved by something, and, since an endless regress is impossible, we must arrive somewhere at something which moves other things without being moved. This unmoved mover is God. It might be objected that this argument involves the eternity of movement, which Catholics reject. This would be an error: it is valid on the hypothesis of the eternity of movement, but is only strengthened by the opposite hypothesis, which involves a beginning, and therefore a First Cause.

In the Summa Theologiae, five proofs of God's existence are given. First, the argument of the unmoved mover, as above. Second, the argument of the First Cause, which again depends upon the impossibility of an infinite regress. Third, that there must be an ultimate source of all necessity; this is much the same as the second argument. Fourth, that we find various perfections in the world, and that these must have their source in something completely perfect. Fifth, that we find even lifeless things serving a purpose, which must be that of some being outside them, since only living things can have an internal purpose.

To return to the Summa contra Gentiles, having proved the existence of God, we can now say many things about Him, but these are all, in a sense, negative; God's nature is only known to us through what is not. God is eternal, since He is unmoved; He is unchanging, since He contains no passive potentiality. David of Dinant (a materialistic pantheist of the early thirteenth century) 'raved' that God is the same as primary matter; this is absurd, since primary matter is pure passivity, and God is pure activity. In God, there is no composition, therefore He is not a body, because bodies have parts.

God is His own essence, since otherwise He would not be simple, but would be compounded of essence and existence. (This point is important.) In God, essence and existence are identical. There are no accidents in God. He cannot be specified by any substantial difference; He is not in any genus; He cannot be defined. But He lacks not the excellence of any genus. Things are in some ways like God, in others not. It is more fitting to say that things are like God than that God is like things.

God is good, and is His own goodness; He is the good of every good. He is intelligent, and His act of intelligence is His essence. He understands by His essence, and understands Himself perfectly. (John the Scot, it will be remembered, thought otherwise.)

Although there is no composition in the divine intellect, God understands many things. This might seem a difficulty, but the things that He understands have no distinct being in Him. Nor do they exist per se, as Plato thought, because forms of natural things cannot exist or be understood apart from matter. Nevertheless, God must understand forms before creating. The solution of this difficulty is as follows: 'The concept of the divine intellect, according as He understands Himself, which concept is His Word, is the likeness not only of God Himself understood, but also of all the things of which the divine essence is the likeness. Accordingly many things can be understood by God, by one intelligible species which is the divine essence, and by one understood intention which is the divine Word.'3 Every form, so far as it is something positive, is a perfection. God's intellect includes in His

essence what is proper to each thing, by understanding where it is like Him and where unlike; for instance life, not knowledge, is the essence of a plant, and knowledge, not intellect, is the essence of an animal. Thus a plant is like God in being alive, but unlike in not having knowledge; an animal is like God in having knowledge, but unlike in not having intellect. It is always by a negation that a creature differs from God.

God understands all things at the same instant. His knowledge is not a habit, and is not discursive or argumentative. God is truth. (This is to be understood literally.)

We come now to a question which had already troubled both Plato and Aristotle. Can God know particular things, or does He only know universals and general truths? A Christian, since he believes in Providence, must hold that God knows particular things; nevertheless, there are weighty arguments against this view. St Thomas enumerates seven such arguments, and then proceeds to refute them. The seven arguments are as follows:

1. Singularity being signate matter, nothing immaterial can know it.

2. Singulars do not always exist, and cannot be known when they do not exist; therefore they cannot be known by an unchanging being.

3. Singulars are contingent, not necessary; therefore there can be no certain knowledge of them except when they exist.

4. Some singulars are due to volitions, which can only be known to the person willing.

5. Singulars are infinite in number, and the infinite as such is unknown.

6. Singulars are too petty for God's attention.

7. In some singulars there is evil, but God cannot know evil.

Aquinas replies that God knows singulars as their cause; that He knows things that do not yet exist, just as an artificer does when he is making something; that He knows future contingents, because He sees each thing in time as if present, He Himself being not in time; that He knows our minds and secret wills, and that He knows an infinity of things, although we cannot do so. He knows trivial things, because nothing is wholly trivial, and everything has some nobility; otherwise God would know only Himself. Moreover the order of the universe is very noble, and this cannot be known without knowing even the trivial parts. Finally, God knows evil things, because knowing anything good involves knowing the opposite evil.

In God there is Will; His Will is His essence, and its principal object is the divine essence. In willing Himself, God wills other things also, for God is the end of all things. He wills even things that are not yet, He wills His own being and goodness, but other things, though He wills them, He does not will necessarily. There is free will in God; a reason can be assigned for His volition, but not a cause. He cannot will things impossible in themselves; for example, He cannot make a contradiction true. The Saint's example of something beyond even divine power is not an altogether happy one; he says that God could not make a man be an ass.

In God are delight and joy and love; God hates nothing, and possesses the contemplative and active virtues. He is happy, and is His own happiness.

We come now (in Book II) to the consideration of creatures. This is useful for refuting errors against God. God created the world out of nothing, contrary to the opinions of the ancients. The subject of the things that God cannot do is resumed. He cannot be a body, or change Himself; He cannot fail; He cannot be weary, or forget, or repent, or be angry or sad; He cannot make a man have no soul, or make the sum of the angles of a triangle be not two right angles. He cannot undo the past, commit sins, make another God, or make Himself not exist.

Book II is mainly occupied with the soul in man. All intellectual substances are immaterial and incorruptible; angels have no bodies, but in men the soul is united to a body. It is the form of the body, as in Aristotle. There are not three souls in man, but only one. The whole soul is present entire in every part of the body. The souls of animals, unlike those of men, are not immortal. The intellect is part of each man's soul; there is not, as Averroes maintained, only one intellect, in which various men participate. The soul is not transmitted with the semen, but is created afresh with each man. There is, it is true, a difficulty: when a man is born, out of wedlock, this seems to make God an accomplice in adultery. This objection, however, is only specious. (There is a grave objection, which troubled St Augustine, and that is as to the transmission of original sin. It is the soul that sins, and if the soul is not transmitted, but created afresh, how can it inherit the sin of Adam? This is not discussed.)

In connection with the intellect, the problem of universals is discussed. St Thomas's position is that of Aristotle. Universals do not subsist outside the soul, but the intellect, in understanding universals, understands things that are outside the soul.

The Third Book is largely concerned with ethical questions. Evil is unintentional, not an essence, and has an accidental cause which is good. All things tend to be like God who is the end of all things. Human happiness does not consist in carnal pleasures, honour, glory, wealth, worldly power, or goods of the body, and is not seated in the senses. Man's ultimate happiness does not consist in acts of moral virtue, because these are means; it consists in the contemplation of God. But the knowledge of God possessed by the majority does not suffice; nor the knowledge of Him obtained by demonstration; nor even the knowledge obtained by faith. In this life, we cannot see God in His essence, or have ultimate happiness; but hereafter we shall see Him face to face. (Not literally, we are warned, because God has no face.) This will happen, not by our natural power, but by the divine light; and even then, we shall not see all of Him. By this vision we become partakers of eternal life, i.e. of life outside time.

Divine Providence does not exclude evil, contingency, free will, chance or luck. Evil comes through second causes, as in the case of a good artist with bad tools.

Angels are not all equals; there is an order among them. Each angel is the sole specimen of his species, for, since angels have no bodies, they can only be distinct through specific differences, not through position in space.

Astrology is to be rejected, for the usual reasons. In answer to the question 'Is there such a thing as fate?' Aquinas replies that we might give the name 'fate' to the order impressed by Providence, but it is wiser not to do so, as 'fate' is a pagan word. This leads to an argument that prayer is useful although Providence is unchangeable. (I have failed to follow this argument.) God sometimes works miracles, but no one else can. Magic, however, is possible with the help of demons; this is not properly miraculous, and is not by the help of the stars.

Divine law directs us to love God; also, in a lesser degree, our neighbour. It forbids fornication, because the father should stay with the mother while the children are being reared. It forbids birth control, as being against nature; it does not, however, on this account forbid life-long celibacy. Matrimony should be indissoluble, because the father is needed in the education of the children, both as more rational than the mother, and as having more physical strength when punishment is required. Not all carnal intercourse is sinful, since it is natural; but to think the married state as good as continence is to fall into the heresy of Jovinian. There must be strict monogamy; polygyny is unfair to women, and polyandry makes paternity uncertain. Incest is to be forbidden because it would complicate family life. Against brother-sister incest there is a very curious argument: that if the love of husband and wife were combined with that of brother and sister, mutual attraction would be so strong as to cause unduly frequent intercourse.

All these arguments on sexual ethics, it is to be observed, appeal to purely rational considerations, not to divine commands and prohibitions. Here, as throughout the first three books, Aquinas is glad, at the end of a piece of reasoning, to quote texts showing that reason has led him to a conclusion in harmony with the Scriptures, but he does not appeal to authority until his result has been reached.

There is a most lively and interesting discussion of voluntary poverty, which, as one might expect, arrives ultimately at a conclusion in harmony with the principles of the mendicant Orders, but states the objections with a force and realism which shows them to be such as he had actually heard urged by the secular clergy.

He then passes on to sin, predestination, and election, on which his view is broadly that of Augustine. By mortal sin a man forfeits his last end to all eternity, and therefore eternal punishment is his due. No man can be freed from sin except by grace, and yet the sinner is to be blamed if he is not converted. Man needs grace to persevere in good, but no one can merit divine assistance. God is not the cause of sinning, but some He leaves in sin, while others He delivers from it. As regards predestination, St Thomas seems to hold, with St Augustine, that no reason can be given why some are elected and go to heaven, while others are left reprobate and go to hell. He holds also that no man can enter heaven unless he has been baptized. This is not one of the truths that can be proved by the unaided reason; it is revealed in John iii. 5.4

The fourth book is concerned with the Trinity, the Incarnation, the supremacy of the Pope, the sacraments, and the resurrection of the body. In the main, it is addressed to theologians rather than philosophers, and I shall therefore deal with it briefly.

There are three ways of knowing God: by reason, by revelation, and by intuition of things previously known only by revelation. Of the third way, however, he says almost nothing. A writer inclined to mysticism would have said more of it than of either of the others, but Aquinas's temperament is ratiocinative rather than mystical.

The Greek Church is blamed for denying the double procession of the Holy Ghost and the supremacy of the Pope. We are warned that, although Christ was conceived of the Holy Ghost, we must not suppose that He was the son of the Holy Ghost according to the flesh.

The sacraments are valid even when dispensed by wicked ministers. This was an important point in Church doctrine. Very many priests lived in mortal sin, and pious people feared that such priests could not administer the sacraments. This was awkward; no one could know if he was really married, or if he had received valid absolution. It led to heresy and schism, since the puritanically minded sought to establish a separate priesthood of more impeccable virtue. The Church, in consequence, was obliged to assert with great emphasis that sin in a priest did not incapacitate him for the performance of his functions.

One of the last questions discussed is the resurrection of the body. Here, as elsewhere, Aquinas states very fairly the arguments that have been brought against the orthodox position. One of these, at first sight, offers great difficulties. What is to happen, asks the Saint, to a man who never, throughout his life, ate anything but human flesh, and whose parents did likewise? It would

seem unfair to his victims that they should be deprived of their bodies at the last day as a consequence of his greed; yet, if not, what will be left to make up his body? I am happy to say that this difficulty, which might at first sight seem insuperable, is triumphantly met. The identity of the body, St Thomas points out, is not dependent on the persistence of the same material particles; during life, by the processes of eating and digesting, the matter composing the body undergoes perpetual change. The cannibal may, therefore, receive the same body at the resurrection, even if it is not composed of the same matter as was in his body when he died. With this comforting thought we may end our abstract of the Summa contra Gentiles.

In its general outlines, the philosophy of Aquinas agrees with that of Aristotle, and will be accepted or rejected by a reader in the measure in which he accepts or rejects the philosophy of the Stagyrite. The originality of Aquinas is shown in his adaptation of Aristotle to Christian dogma, with a minimum of alteration. In his day he was considered a bold innovator; even after his death many of his doctrines were condemned by the universities of Paris and Oxford. He was even more remarkable for systematizing than for originality. Even if every one of his doctrines were mistaken, the Summa would remain an imposing intellectual edifice. When he wishes to refute some doctrine, he states it first, often with great force, and almost always with an attempt at fairness. The sharpness and clarity with which he distinguishes arguments derived from reason and arguments derived from revelation are admirable. He knows Aristotle well, and understands him thoroughly, which cannot be said of any earlier Catholic philosopher.

These merits, however, seem scarcely sufficient to justify his immense reputation. The appeal to reason is, in a sense, insincere, since the conclusion to be reached is fixed in advance. Take, for example, the indissolubility of marriage. This is advocated on the ground that the father is useful in the education of the children, (a) because he is more rational than the mother, (b) because, being stronger, he is better able to inflict physical punishment. A modern educator might retort (a) that there is no reason to suppose men in general more rational than women, (b) that the sort of punishment that requires great physical strength is not desirable in education. He might go on to point out that fathers, in the modern world, have scarcely any part in education. But no follower of St Thomas would, on that account, cease to believe in lifelong monogamy, because the real grounds of belief are not those which are alleged.

Or take again the arguments professing to prove the existence of God. All these, except the one from teleology in lifeless things, depend upon the supposed impossibility of a series having no first term. Every mathematician knows that there is no such impossibility; the series of negative integers ending with minus one is an instance to the contrary. But here again no Catholic is likely to abandon belief in God even if he becomes convinced that St Thomas's arguments are bad; he will invent other arguments, or take refuge in revelation.

The contentions that God's essence and existence are one and the same, that God is His own goodness, His own power, and so on, suggest a confusion, found in Plato, but supposed to have been avoided by Aristotle, between the manner of being of particulars and the manner of being of universals. God's essence is, one must suppose, of the nature of universals, while His existence is not. It is difficult to state this difficulty satisfactorily, since it occurs within a logic that can no longer be accepted. But it points clearly to some kind of syntactical confusion, without which much of the argumentation about God would lose its plausibility.

There is little of the true philosophic spirit in Aquinas. He does not, like the Platonic Socrates, set out to follow wherever the argument may lead. He is not engaged in an enquiry, the result of which it is impossible to know in advance. Before he begins to philosophize, he already knows the truth; it is declared in the Catholic faith. If he can find apparently rational arguments for some parts of the faith, so much the better; if he cannot, he need only fall back on revelation. The finding of arguments for a conclusion given in advance is not philosophy, but special pleading. I cannot, therefore, feel that he deserves to be put on a level with the best philosophers either of Greece or of modern times.

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