The military conflict between the Frederick and the papacy, brought the emperor's troops into the monastery in 1239, and the 14-year-old was sent on to the University of Naples. The university had been founded by Frederick for the secular education of his court functionaries. It was in Naples that Thomas was introduced to the work of the Greek philosophers, Plato and Aristotle, as well as the Muslim scholar Ibn Rushd and the Jewish scholar Moses Maimonides. At this time the Catholic Church was opposed to studying early Greek philosophers. Amalric of Bena taught philosophy and theology at the University of Paris; his lectures developing the philosophy of Aristotle attracted a large group of students. In 1204 Pope Innocent III condemned him as a heretic. his doctrines were condemned by the university, and he was removed from the teaching staff. His death in 1207 "was caused, it is said, by grief at the humiliation to which he had been subjected". In 1209 ten of his followers were burnt before the gates of Paris, and Amalric's own body was exhumed and burnt. (4)

Thomas also came under the influence of local preachers in Naples, who was part of the active effort by the Dominican order to recruit new followers. The Dominican Order was Catholic religious order founded by the Spanish priest Dominic of Caleruega in about 1205. It began in the south of France in an effort to convert the Cathars, a Christian religious sect which the Roman Catholic Church deemed heretical. Dominic argued that only preachers who displayed real sanctity, humility and asceticism could win over convinced Cathar believers. The idea of two gods or principles, one good and the other evil, was central to Cathar beliefs. Cathars believed that the good God was the God of the New Testament and the creator of the spiritual realm. They believed the evil God was the God of the Old Testament, creator of the physical world whom many Cathars, and particularly their persecutors, identified as Satan. (5)

This campaign was not very successful and the Inquisition was established in 1233 to uproot the Cathars. Those who refused to recant were hanged, or burnt at the stake. On 13th May 1239, 183 men and women convinced of Catharism were burned at the stake. From May 1243 to March 1244, the Cathar fortress of Montségur was besieged by the troops of the seneschal of Carcassonne and the archbishop of Narbonne. On 16th March 1244, over 200 Cathar Perfects were burnt near the foot of the castle. It is believed that a total of 325 Cathars were executed in 1244. (6)

Despite their lack of success with the Cathars the Dominican movement continued to grow. Whereas the Benedictines were men of the land, communally rich, aristocrats, representatives of the established order. Dominicans were men of the new towns not considered to be very respectable. According to Brian Davies, the author of The Thought of Thomas Aquinas (1992) the begging friars went "out two by two to preach in town after town, taking nothing for their journey but a staff: no bread, no wallet, no money in their belt, wearing sandals and only one tunic." (7)

Aquinas, joined the Dominicans in April 1244. His family were horrified and on his mother's orders, Thomas was kidnapped by a squad of Frederick II's soldiers, including his brother Rinaldo, and kept prisoner for over a year. At one point, two of his brothers resorted to the measure of hiring a prostitute to seduce him. According to Renn Dickson Hampden Thomas drove her away wielding a fire iron and two angels appeared to him as he slept and strengthened his determination to remain celibate. Theodora accepting defeat, arranged for Thomas to escape at night through his window. (8)

Thomas Aquinas was sent to Paris. The distance from Naples to Paris is over 1,000 miles. Friars were forbidden from travelling on horseback so it is possible that he may have walked all the way. In Paris he attended lectures, notably by the Dominican, Albertus Magnus, one of the greatest scholars of the Middle Ages. These lectures included discussions on Aristotle. Study of Aristotle had been banned at the University of Paris in 1215 and had been periodically renewed, had only recently been allowed. In 1248 he accompanied Magnus to Cologne to set up a new study centre. (9)

In 1252 Aquinas returned to Paris and began writing textbooks that he used in his teaching. This was to occupy his time for the next twenty years. Aquinas lectures were normally exercises in reading a text in common. Aquinas (known as the master) alone would have an actual copy of the text before him. This thesis was usually written by Aquinas. Students were encouraged to ask questions of the material. These questions would be answered there and then. After a certain amount of time - maybe, on the following day - Aquinas would deliver a summing-up in which he would be required to give a definitive defence of his thesis, taking into account the whole range of objections that had been brought against it. "The summing-up would consist of an argument in depth for the thesis, to which would be appended definitive explanations of how his argument answers the objections with which the disputation started. Later still, at more leisure, the master might be able to edit such disputations for publication." (10)

Over the next twenty-five years, Thomas Aquinas wrote or dictated over eight million words: two million of commentary on the Bible; a million on Aristotle; with the rest divided between records of the disputations at which he presided, many short works, and three large volumes of Christian doctrine. Taking students through the Bible was Thomas's principal duty. Two of these commentaries, The Book of Job (1261-65) and the Gospel of John (1270-72) are considered to be especially important. (11)

This method was not intended to reach compromise or supposed consensus. It encouraged students to discover the strengths as well as the weaknesses of opposing views; but the aim was to work out the truth by considering and eliminating error, however common or plausible or supported by authority. As Bertrand Russell pointed out, that "Thomas Aquinas... is concerned to establish the truth of the Christian religion by arguments addressed to a reader supposed to be not already a Christian." (12)

Thomas Aquinas began his first important work, Commentary on the Sentences of Peter Lombard in about 1252. Peter Lombard had produced a book on theology in the 12th century. In the book Aquinas dealt with possible abuses of political power: "With regard to the abuse of authority, this also may come about in two ways. First, when what is ordered by an authority is opposed to the object for which that authority was constituted (if, for example, some sinful action is commanded or one which is contrary to virtue, when it is precisely for the protection and fostering of virtue that authority is instituted). In such a case, not only is there no obligation to obey the authority, but one is obliged to disobey it, as did the holy martyrs who suffered death rather than obey the impious commands of tyrants. Secondly, when those who bear such authority command things which exceed the competence of such authority; as, for example, when a master demands payment from a servant which the latter is not bound to make, and other similar cases. In this instance the subject is free to obey or disobey." (13)

His style of teaching can be seen in De Potentia (On Power). He responds to the question: Is There but One Principle of Creation? "It is on account neither of God's weakness nor ignorance that evil comes into the world, but rather it is due to the order of his wisdom and the greatness of his goodness that diverse grades of goodness occur in things, many of which would be lacking if no evil were permitted. Indeed, the good of patience would not exist without the evil of persecution; nor the good of preservation of life in a lion if not for the evil of the destruction of the animals on which it lives." (14)

Thomas Aquinas work gradually became acceptable to the Church authorities. In February 1265 the newly elected Pope Clement IV summoned Thomas to Rome to serve as papal theologian. This same year he was appointed to teach at the studium conventuale at the Roman convent of Santa Sabina. Prior to this time the Roman Province had offered no specialized education of any sort, no arts, no philosophy; only simple convent schools, with their basic courses in theology for resident friars. However, Thomas taught at Santa Sabina at the full range of philosophical subjects, both moral and natural. (15)

In Two Precepts of Charity (1273). He argues that: "Three things are necessary for the salvation of man: to know what he ought to believe; to know what he ought to desire; and to know what he ought to do." After explaining his views on charity he deals with the objections by quoting from the Bible: "To do good is more than to avoid evil, and therefore the positive precepts virtually include the negative precepts. Nevertheless we find explicit precepts against the vices contrary to charity: for, against hatred it is written (Leviticus 12:17): "Thou shalt not hate thy brother in thy heart"; against sloth (Sirach 6:26): "Be not grieved with her bands"; against envy (Galatians 5:26): "Let us not be made desirous of vainglory, provoking one another, envying one another"; against discord (1 Corinthians 1:10): "That you all speak the same thing, and that there be no schisms among you"; and against scandal (Romans 14:13): "That you put not a stumbling-block or a scandal in your brother's way." (16)

Bertrand Russell in his book, History of Western Philosophy (1946) argues that Aquinas greatest contribution to philosophy was in the way he incorporated the ideas of Aristotle into Christianity: "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.... 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." (17)

Aquinas began Summa Contra Gentiles (Book on the truth of the Catholic faith against the errors of the unbelievers) in 1259 and took five years to write. In the book Aquinas attacked the Muslim religion: "Muhammad seduced the people by promises of carnal pleasure to which the concupiscence of the flesh goads us. His teaching also contained precepts that were in conformity with his promises, and he gave free rein to carnal pleasure. In all this, as is not unexpected, he was obeyed by carnal men. As for proofs of the truth of his doctrine, he brought forward only such as could be grasped by the natural ability of anyone with a very modest wisdom. Indeed, the truths that he taught he mingled with many fables and with doctrines of the greatest falsity. He did not bring forth any signs produced in a supernatural way, which alone fittingly gives witness to divine inspiration; for a visible action that can be only divine reveals an invisibly inspired teacher of truth. On the contrary, Muhammad said that he was sent in the power of his arms - which are signs not lacking even to robbers and tyrants. What is more, no wise men, men trained in things divine and human, believed in him from the beginning, Those who believed in him were brutal men and desert wanderers, utterly ignorant of all divine teaching, through whose numbers Muhammad forced others to become his followers by the violence of his arms. Nor do divine pronouncements on the part of preceding prophets offer him any witness. On the contrary, he perverts almost all the testimonies of the Old and New Testaments by making them into fabrications of his own, as can be seen by anyone who examines his law. It was, therefore, a shrewd decision on his part to forbid his followers to read the Old and New Testaments, lest these books convict him of falsity. It is thus clear that those who place any faith in his words believe foolishly." (18)

Thomas Aquinas, most important work, The Summa Theologiae (The Theology) was started in 1265 and continued to be written to just before his death. The American philosopher, James Francis Ross, has argued that "one of the classics of the history of philosophy and one of the most influential works of Western literature." (19) Anthony Kenny claims that the work shows that "Thomas Aquinas is one of the dozen greatest philosophers of the western world." (20) Fergus Kerr takes the view that "the Summa Theologiae counts among the half dozen great works of Catholic Christian theology." (21) Joseph Louis Perrier believes it is Aquinas' "most perfect work, the fruit of his mature years, in which the thought of his whole life is condensed." (22)

Bertrand Russell that even " if every one of his doctrines were mistaken, the Summa would remain an imposing intellectual edifice." He then adds: "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. 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." (23)

The Summa is structured into three Parts which are subdivided into 614 Questions. This in turn, are subdivided into 3,125 Articles. Questions are specific topics of discussion, while their articles are even more specific questions, facets of the parent question. For example, in Part I, Question 1, Article I, he states: "It was necessary for our salvation that there be a knowledge revealed by God, besides philosophical science built up by human reason. Firstly, indeed, because the human being is directed to God, as to an end that surpasses the grasp of his reason. "The eye hath not seen, O God, besides Thee, what things Thou hast prepared for them that wait for Thee" (Isaiah 64:4). But the end must first be known by men who are to direct their thoughts and actions to the end. Hence it was necessary for the salvation of man that certain truths which exceed human reason should be made known to him by divine revelation." (24)

Thomas Aquinas introduced his famous "five ways" of demonstrating God's existence, which he happily takes from the philosophers of antiquity, are not an attempt to refute atheism but an effort of faith seeking understanding of itself. "(1) motion in the world is explicable only if there is a first unmoved mover; (2) the chain of efficient causes in the world presupposes an uncaused cause; (3) contingent beings must depend on a necessary being; (4) the degrees of reality and goodness in the world must be approximations to a self-standing maximum of reality and goodness; and (5) the empirically obvious teleology (the explanation of phenomena in terms of the purpose they serve rather than of the cause by which they arise) of non-conscious agents in the universe entails the existence of an intelligent universal principle. These five arguments, for which Thomas claims no originality, demonstrate, from features of the world, that there is a source and goal of everything that exists." (25)

One of arguments he makes for the existence of God: "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." (26)

One of his critics uses mathematics to refute this. "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." (27)

Timothy McDermot admits: "Thomas Aquinas, it is true, is not so much interested in the bases of arithmetic as in the bases for belief in God, and – as a Christian theologian – interested too in defending his Christian faith against unbelievers. But he thought that, as a consequence, one of his greatest tasks was to distinguish between beliefs that were philosophical provable ('discoverable by natural reason', as he puts it), assertions of faith which, though unproven, were philosophically sound in the sense of not disprovable, and beliefs demonstrably false." (28)

The Just War

In The Summa Theologiae Thomas Aquinas attempts to answer the question: "Whether it is always sinful to wage war? At first he looks at the evidence that suggests war is sinful: Objection 1: "It would seem that it is always sinful to wage war. Because punishment is not inflicted except for sin. Now those who wage war are threatened by Our Lord with punishment, according to Matthew 26:52: 'All that take the sword shall perish with the sword.' Therefore all wars are unlawful." Objection 2: "Further, whatever is contrary to a Divine precept is a sin. But war is contrary to a Divine precept, for it is written (Matthew 5:39): 'But I say to you not to resist evil'; and (Romans 12:19): 'Not revenging yourselves, my dearly beloved, but give place unto wrath.' Therefore war is always sinful." Objection 3: "Further, nothing, except sin, is contrary to an act of virtue. But war is contrary to peace. Therefore war is always a sin." Objection 4. "Further, the exercise of a lawful thing is itself lawful, as is evident in scientific exercises. But warlike exercises which take place in tournaments are forbidden by the Church, since those who are slain in these trials are deprived of ecclesiastical burial. Therefore it seems that war is a sin in itself. On the contrary, Augustine says in a sermon on the son of the centurion: 'If the Christian Religion forbade war altogether, those who sought salutary advice in the Gospel would rather have been counselled to cast aside their arms, and to give up soldiering altogether. On the contrary, they were told: 'Do violence to no man... and be content with your pay' (Luke 3:14). If he commanded them to be content with their pay, he did not forbid soldiering."

Aquinas replied to this question in the following way: "I answer that, In order for a war to be just, three things are necessary. First, the authority of the sovereign by whose command the war is to be waged. For it is not the business of a private individual to declare war, because he can seek for redress of his rights from the tribunal of his superior. Moreover it is not the business of a private individual to summon together the people, which has to be done in wartime. And as the care of the common weal is committed to those who are in authority, it is their business to watch over the common weal of the city, kingdom or province subject to them. And just as it is lawful for them to have recourse to the sword in defending that common weal against internal disturbances, when they punish evil-doers, according to the words of the Apostle (Romans 13:4): "He beareth not the sword in vain: for he is God's minister, an avenger to execute wrath upon him that doth evil"; so too, it is their business to have recourse to the sword of war in defending the common weal against external enemies. Hence it is said to those who are in authority (Psalm 81:4): "Rescue the poor: and deliver the needy out of the hand of the sinner"; and for this reason Augustine says (Contra Faust. xxii, 75): "The natural order conducive to peace among mortals demands that the power to declare and counsel war should be in the hands of those who hold the supreme authority."

Secondly, a just cause is required, namely that those who are attacked, should be attacked because they deserve it on account of some fault. Wherefore Augustine says (QQ. in Hept., qu. x, super Jos.): "A just war is wont to be described as one that avenges wrongs, when a nation or state has to be punished, for refusing to make amends for the wrongs inflicted by its subjects, or to restore what it has seized unjustly."

Thirdly, it is necessary that the belligerents should have a rightful intention, so that they intend the advancement of good, or the avoidance of evil. Hence Augustine says (De Verb. Dom. [The words quoted are to be found not in St. Augustine's works, but Can. Apud. Caus. xxiii, qu. 1): "True religion looks upon as peaceful those wars that are waged not for motives of aggrandizement, or cruelty, but with the object of securing peace, of punishing evil-doers, and of uplifting the good." For it may happen that the war is declared by the legitimate authority, and for a just cause, and yet be rendered unlawful through a wicked intention. Hence Augustine says (Contra Faust. xxii, 74): "The passion for inflicting harm, the cruel thirst for vengeance, an unpacific and relentless spirit, the fever of revolt, the lust of power, and such like things, all these are rightly condemned in war." (29)

Fergus Kerr points out that the early Christians regarded military life, with its commitment to shedding blood on occasion, as unacceptable. In the 5th century Augustine had attempted to explain the acceptance of the violence carried out by the Roman Army. By the 13th century, even the Roman Catholic Church resorted to violence to deal with heretics. "He (Thomas Aquinas) sets out three conditions for making war lawfully. First, only a prince may initiate military action. Second, there must be a just cause: the enemy must have violated the rights of one's community. Third, the intention of those making war must be right; they must intend to promote good or avoid evil. In effect, going to war to redress an injury must not be likely to do more harm than leaving the injury unaddressed." (30)

Anthony Grayling has questioned how much relevance Aquinas's views on war have today. "Does this justify using nuclear weapons or poison gas? This point raises the separate but profoundly important question of what counts as acting justly once one is engaged in fighting a just war… One good example of a just cause for war is defence against aggression; another is going to the aid of victims of aggression. Does this mean it is also just to launch pre-emptive military action against a potential aggressor? Wars caused by religious feeling and differences, even if the casual link is indirect, are never justifiable. Whatever the excuse given for such wars, they share the same root cause: divisions generated by differences in belief systems which, because they are not about matters of verifiable or even rationally plausible fact, are all the more passionately – hot-headed, unreasoningly, violently – espoused." (31)

In 1277 Étienne Tempier, the bishop of Paris, condemned the teachings of Aquinas. He argued that God's absolute power transcended any principles of logic that Aristotle or some other philosopher might place on it. More specifically, it contained a list of 219 propositions that the bishop had determined to violate the omnipotence of God, and included in this list were twenty of Aquinas propositions. Their inclusion badly damaged Thomas's reputation for many years. (32)

The University of Oxford also condemned the teachings of Aquinas. However, Bertrand Russell , condemns him for his conservatism and rejects the idea that he was a philosopher: "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. 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." (33)

In December 1273, Thomas Aquinas decided to write no more: "Everything I have written seems like straw by comparison with what I have seen and what has been revealed to me." (34) Presumably he had some kind of mystical experience. Others have claimed he had suffered a stroke. He died on 7th March 1274. In 1369, Pope Urban V, asked for his bones to be moved to Toulouse. (35)

The papacy gradually found Aquinas's philosophy more acceptable. In 1567, Pope Pius V proclaimed St. Thomas Aquinas a Doctor of the Church and ranked his feast with those of the four great Latin fathers: Augustine of Hippo, Aurelius Ambrose, Jerome and Gregory of Nazianzus. At the Council of Trent, the 19th ecumenical council of the Catholic Church that had been prompted by the Protestant Reformation, Aquinas had the honor of having his The Summa Theologiae placed on the altar alongside the Bible. (36)

Anthony Gottlieb, the author of The Dream of Reason: A History of Philosophy from the Greeks to the Renaissance (2000) argues: "Thinkers such as St Thomas Aquinas set about the daunting but necessary project of trying to combine Christianity with the latest developments – that is, with Aristotelianism. Even such well-intentioned and eminently pious efforts were censored in some quarters in the early days, though the teachings of Aquinas were upheld by the important theological Council of Lyons in 1274. Thomism, as Aquinas' synthesis came to be known, was clearly the crowning achievement of Christian philosophizing." (37)

On 4th August 1879, Pope Leo XIII stated that Thomas Aquinas's theology was a definitive exposition of Catholic doctrine. Thus, he directed the clergy to take the teachings of Thomas as the basis of their theological positions. He also decreed that all Catholic seminaries and universities must teach Thomas's doctrines, and where Thomas did not speak on a topic, the teachers were "urged to teach conclusions that were reconcilable with his thinking." In 1880, Saint Thomas Aquinas was declared patron of all Catholic educational establishments. (38)

The Middle Ages

The Normans

The Tudors

The English Civil War

Industrial Revolution

First World War

Russian Revolution

Nazi Germany

United States: 1920-1945

(1) Fergus Kerr, Thomas Aquinas (2013) page 3

(2) Timothy McDermott, Aquinas: Selected Philosophical Writings (1993) page xiii

(3) Martin Grabmann, Thomas Aquinas: His Personality and Thought (2006) page 2

(4) Encyclopædia Britannica, entry for Amalric of Bena (1911)

(5) Margaret C. Schaus, Women And Gender in Medieval Europe: An Encyclopedia (2006) page 114

(6) Jonathan Sumption, The Albigensian Crusade (1999) pages 238-340

(7) Brian Davies, The Thought of Thomas Aquinas (1992) page 2

(8) Renn Dickson Hampden, The Life of Thomas Aquinas (1848) pages 27-28

(9) Fergus Kerr, Thomas Aquinas (2013) page 13

(10) imothy McDermott, Aquinas: Selected Philosophical Writings (1993) page xviii

(11) Fergus Kerr, Thomas Aquinas (2013) page 20

(12) Bertrand Russell, History of Western Philosophy (1946) pages 444

(13) Thomas Aquinas, Commentary on the Sentences of Peter Lombard (c. 1252)

(14) Thomas Aquinas, De Potentia (c.1265) Question 3, Article 6, Answer 4

(15) Jean-Pierre Torrell, Saint Thomas Aquinas (2005) pages 129-132

(16) Two Precepts of Charity (1273) Article III: Whether two precepts of charity suffice? Reply to Objection 3

(17) Bertrand Russell, History of Western Philosophy (1946) page 452

(18) Thomas Aquinas, Summa Contra Gentiles (c. 1274) Book 1: Chapter 6

(19) James Francis Ross, The Classics of Western Philosophy: A Reader's Guide (2003) page 165

(20) Anthony Kenny, Aquinas: A Collection of Critical Essays (1969) page 1

(21) Fergus Kerr, Thomas Aquinas (2013) page 31

(22) Joseph Louis Perrier, The Revival of Scholastic Philosophy in the Nineteenth Century (1909) page 149

(23) Bertrand Russell, History of Western Philosophy (1946) page 453

(24) Thomas Aquinas, Summa Theologica (1265–1274) Part I, Question 1, Article 1

(25) Fergus Kerr, Thomas Aquinas (2013) page 39

(26) Thomas Aquinas, Summa Theologica (1265–1274) Part I, Question 2, Article 3

(27) Bertrand Russell, History of Western Philosophy (1946) page 453

(28) Timothy McDermott, Aquinas: Selected Philosophical Writings (1993) page xi

(29) Thomas Aquinas, Summa Theologica (1265–1274) Part II, Question 40, Article 1-4

(30) Fergus Kerr, Thomas Aquinas (2013) pages 6-7

(31) Anthony Grayling, Ideas that Matter (2009) pages 532-544

(32) Edward Grant, The Foundations of Modern Science in the Middle Ages (1996) page 81

(33) Bertrand Russell, History of Western Philosophy (1946) page 453

(34) Bernhard Lang, Sacred Games: A History of Christian Worship (1997) page 323

(35) Fergus Kerr, Thomas Aquinas (2013) page 19

(36) Hans Kung, Christian Thinkers (1994) page 114

(37) Anthony Gottlieb, The Dream of Reason: A History of Philosophy from the Greeks to the Renaissance (2000) pages 397-398

(38) Edward Grant, The Foundations of Modern Science in the Middle Ages (1996) page 82