|Saint Thomas Aquinas|
|Doctor of the Church|
Roccasecca, Kingdom of Sicily
|Died||7 March 1274
Fossanova, Papal States
|Venerated in||Catholic Church
|Canonized||18 July 1323, Avignon, Papal States by Pope John XXII|
|Major shrine||Church of the Jacobins, Toulouse, France|
|Feast||28 January (7 March, until 1969)|
|Attributes||The Summa theologiae, a model church, the sun on the chest of a Dominican friar|
|Patronage||Academics; against storms; against lightning; apologists; Aquino, Italy; Belcastro, Italy; book sellers; Catholic academies, schools, and universities; chastity; Falena, Italy; learning; pencil makers; philosophers; publishers; scholars; students; University of Sto. Tomas; Sto. Tomas, Batangas; theologians.|
|Alma mater||Abbey of Monte Cassino
University of Naples
University of Paris
|Metaphysics, logic, theology, mind, epistemology, ethics, politics|
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Saint Thomas Aquinas O.P. (//; Italian: Tommaso d'Aquino, lit. 'Thomas of Aquino'; 1225 – 7 March 1274), was an Italian Dominican friar, Catholic priest, and Doctor of the Church. He was an immensely influential philosopher, theologian, and jurist in the tradition of scholasticism, within which he is also known as the Doctor Angelicus and the Doctor Communis. The name Aquinas identifies his ancestral origins in the county of Aquino in present-day Lazio, where his family held land until 1137.
He was the foremost classical proponent of natural theology and the father of Thomism. His influence on Western thought is considerable, and much of modern philosophy developed or opposed his ideas, particularly in the areas of ethics, natural law, metaphysics, and political theory. Unlike many currents in the Church of the time, Thomas embraced several ideas put forward by Aristotle—whom he called "the Philosopher"—and attempted to synthesize Aristotelian philosophy with the principles of Christianity. The works for which he is best known are the Summa Theologiae and the Summa contra Gentiles. His commentaries on Scripture and on Aristotle form an important part of his body of work. Furthermore, Thomas is distinguished for his eucharistic hymns, which form a part of the Church's liturgy.
The Catholic Church honors Thomas Aquinas as a saint and regards him as the model teacher for those studying for the priesthood, and indeed the highest expression of both natural reason and speculative theology. In modern times, under papal directives, the study of his works was long used as a core of the required program of study for those seeking ordination as priests or deacons, as well as for those in religious formation and for other students of the sacred disciplines (philosophy, Catholic theology, church history, liturgy, and canon law).
Thomas Aquinas is considered one of the Catholic Church's greatest theologians and philosophers. Pope Benedict XV declared: "This (Dominican) Order ... acquired new luster when the Church declared the teaching of Thomas to be her own and that Doctor, honored with the special praises of the Pontiffs, the master and patron of Catholic schools."
- 1 Biography
- 2 Philosophy
- 3 Theology
- 3.1 Revelation
- 3.2 Creation
- 3.3 Just war
- 3.4 Nature of God
- 3.5 Nature of Sin
- 3.6 Nature of the Trinity
- 3.7 Prima causa (first cause)
- 3.8 Nature of Jesus Christ
- 3.9 Goal of human life
- 3.10 Treatment of heretics
- 3.11 Thoughts on afterlife and resurrection
- 4 Modern influence
- 5 Criticism of Aquinas as philosopher
- 6 Works
- 7 See also
- 8 Notes
- 9 References
- 10 Further reading
- 11 External links
Early life (1225–1244)
Thomas was most probably born in the castle of Roccasecca, located in Aquino, old county of the Kingdom of Sicily (present-day Lazio region, Italy), c.1225. According to some authors[who?], he was born in the castle of his father, Landulf of Aquino. Though he did not belong to the most powerful branch of the family, Landulf of Aquino was a man of means. As a knight in the service of King Roger II, he held the title miles. Thomas' mother, Theodora, belonged to the Rossi branch of the Neapolitan Caracciolo family. Landulf's brother Sinibald was abbot of the first Benedictine monastery at Monte Cassino. While the rest of the family's sons pursued military careers, the family intended for Thomas to follow his uncle into the abbacy;. This would have been a normal career path for a younger son of southern Italian nobility.
At the age of five Thomas began his early education at Monte Cassino but after the military conflict between the Emperor Frederick II and Pope Gregory IX spilled into the abbey in early 1239, Landulf and Theodora had Thomas enrolled at the studium generale (university) recently established by Frederick in Naples. It was here that Thomas was probably introduced to Aristotle, Averroes and Maimonides, all of whom would influence his theological philosophy. It was also during his study at Naples that Thomas came under the influence of John of St. Julian, a Dominican preacher in Naples, who was part of the active effort by the Dominican order to recruit devout followers. There his teacher in arithmetic, geometry, astronomy, and music was Petrus de Ibernia.
At the age of nineteen Thomas resolved to join the recently founded Dominican Order. Thomas' change of heart did not please his family. In an attempt to prevent Theodora's interference in Thomas' choice, the Dominicans arranged to move Thomas to Rome, and from Rome, to Paris. However, while on his journey to Rome, per Theodora's instructions, his brothers seized him as he was drinking from a spring and took him back to his parents at the castle of Monte San Giovanni Campano.
Thomas was held prisoner for about one year in the family castles at Monte San Giovanni and Roccasecca in an attempt to prevent him from assuming the Dominican habit and to push him into renouncing his new aspiration. Political concerns prevented the Pope from ordering Thomas' release, which had the effect of extending Thomas' detention. Thomas passed this time of trial tutoring his sisters and communicating with members of the Dominican Order. Family members became desperate to dissuade Thomas, who remained determined to join the Dominicans. At one point, two of his brothers resorted to the measure of hiring a prostitute to seduce him. According to legend Thomas drove her away wielding a fire iron. That night two angels appeared to him as he slept and strengthened his determination to remain celibate.
By 1244, seeing that all of her attempts to dissuade Thomas had failed, Theodora sought to save the family's dignity, arranging for Thomas to escape at night through his window. In her mind, a secret escape from detention was less damaging than an open surrender to the Dominicans. Thomas was sent first to Naples and then to Rome to meet Johannes von Wildeshausen, the Master General of the Dominican Order.
Paris, Cologne, Albert Magnus, and first Paris regency (1245–1259)
In 1245 Thomas was sent to study at the Faculty of the Arts at the University of Paris, where he most likely met Dominican scholar Albertus Magnus, then the Chair of Theology at the College of St. James in Paris. When Albertus was sent by his superiors to teach at the new studium generale at Cologne in 1248, Thomas followed him, declining Pope Innocent IV's offer to appoint him abbot of Monte Cassino as a Dominican. Albertus then appointed the reluctant Thomas magister studentium. Because Thomas was quiet and didn't speak much, some of his fellow students thought he was slow. But Albertus prophetically exclaimed: "You call him the dumb ox, but in his teaching he will one day produce such a bellowing that it will be heard throughout the world."
Thomas taught in Cologne as an apprentice professor (baccalaureus biblicus), instructing students on the books of the Old Testament and writing Expositio super Isaiam ad litteram (Literal Commentary on Isaiah), Postilla super Ieremiam (Commentary on Jeremiah) and Postilla super Threnos (Commentary on Lamentations). Then in 1252 he returned to Paris to study for the master's degree in theology. He lectured on the Bible as an apprentice professor, and upon becoming a baccalaureus Sententiarum (bachelor of the Sentences) devoted his final three years of study to commenting on Peter Lombard's Sentences. In the first of his four theological syntheses, Thomas composed a massive commentary on the Sentences entitled Scriptum super libros Sententiarium (Commentary on the Sentences). Aside from his masters writings, he wrote De ente et essentia (On Being and Essence) for his fellow Dominicans in Paris.
In the spring of 1256 Thomas was appointed regent master in theology at Paris and one of his first works upon assuming this office was Contra impugnantes Dei cultum et religionem (Against Those Who Assail the Worship of God and Religion), defending the mendicant orders, which had come under attack by William of Saint-Amour. During his tenure from 1256 to 1259, Thomas wrote numerous works, including: Questiones disputatae de veritate (Disputed Questions on Truth), a collection of twenty-nine disputed questions on aspects of faith and the human condition prepared for the public university debates he presided over on Lent and Advent; Quaestiones quodlibetales (Quodlibetal Questions), a collection of his responses to questions posed to him by the academic audience; and both Expositio super librum Boethii De trinitate (Commentary on Boethius' De trinitate) and Expositio super librum Boethii De hebdomadibus (Commentary on Boethius' De hebdomadibus), commentaries on the works of 6th-century Roman philosopher Boethius. By the end of his regency, Thomas was working on one of his most famous works, Summa contra Gentiles.
Naples, Orvieto, Rome (1259–1268)
In 1259 Thomas completed his first regency at the studium generale and left Paris so that others in his order could gain this teaching experience. He returned to Naples where he was appointed as general preacher by the provincial chapter of 29 September 1260. In September 1261 he was called to Orvieto as conventual lector responsible for the pastoral formation of the friars unable to attend a studium generale. In Orvieto Thomas completed his Summa contra Gentiles, wrote the Catena aurea (The Golden Chain), and produced works for Pope Urban IV such as the liturgy for the newly created feast of Corpus Christi and the Contra errores graecorum (Against the Errors of the Greeks). Some of the hymns that Thomas wrote for the feast of Corpus Christi are still sung today, such as the Pange lingua, Tantum ergo, and Panis angelicus. Modern scholarship has confirmed that Thomas was indeed the author of these texts, a point that some had contested.
In February 1265 the newly elected Pope Clement IV summoned Aquinas to Rome to serve as papal theologian. This same year he was ordered by the Dominican Chapter of Agnani to teach at the studium conventuale at the Roman convent of Santa Sabina, founded some years before, in 1222. The studium at Santa Sabina now became an experiment for the Dominicans, the Order's first studium provinciale, an intermediate school between the studium conventuale and the studium generale. 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, were functioning in Tuscany and the meridionale during the first several decades of the order's life. But the new studium at Santa Sabina was to be a school for the province", a studium provinciale. Tolomeo da Lucca, an associate and early biographer of Aquinas, tells us that at the Santa Sabina studium Aquinas taught the full range of philosophical subjects, both moral and natural.
While at the Santa Sabina studium provinciale Thomas began his most famous work, the Summa theologiae, which he conceived of specifically as suited to beginning students: "Because a doctor of Catholic truth ought not only to teach the proficient, but to him pertains also to instruct beginners. As the Apostle says in 1 Corinthians 3:1–2, as to infants in Christ, I gave you milk to drink, not meat, our proposed intention in this work is to convey those things that pertain to the Christian religion in a way that is fitting to the instruction of beginners." While there he also wrote a variety of other works like his unfinished Compendium Theologiae and Responsio ad fr. Ioannem Vercellensem de articulis 108 sumptis ex opere Petri de Tarentasia (Reply to Brother John of Vercelli Regarding 108 Articles Drawn from the Work of Peter of Tarentaise). In his position as head of the studium Aquinas conducted a series of important disputations on the power of God, which he compiled into his De potentia. Nicholas Brunacci [1240–1322] was among Aquinas' students at the Santa Sabina studium provinciale and later at the Paris studium generale. In November 1268 he was with Aquinas and his associate and secretary Reginald of Piperno, as they left Viterbo on their way to Paris to begin the academic year. Another student of Aquinas' at the Santa Sabina studium provinciale was Blessed Tommasello da Perugia.
Aquinas remained at the studium at Santa Sabina from 1265 until he was called back to Paris in 1268 for a second teaching regency. With his departure for Paris in 1268 and the passage of time the pedagogical activities of the studium provinciale at Santa Sabina were divided between two campuses. A new convent of the Order at the Church of Santa Maria sopra Minerva had a modest beginning in 1255 as a community for women converts, but grew rapidly in size and importance after being given over to the Dominicans friars in 1275. In 1288 the theology component of the provincial curriculum for the education of the friars was relocated from the Santa Sabina studium provinciale to the studium conventuale at Santa Maria sopra Minerva, which was redesignated as a studium particularis theologiae. This studium was transformed in the 16th century into the College of Saint Thomas (Latin: Collegium Divi Thomæ). In the 20th century the college was relocated to the convent of Saints Dominic and Sixtus and was transformed into the Pontifical University of Saint Thomas Aquinas, Angelicum.
Quarrelsome second Paris regency (1269–1272)
In 1268 the Dominican order assigned Thomas to be regent master at the University of Paris for a second time, a position he held until the spring of 1272. Part of the reason for this sudden reassignment appears to have arisen from the rise of "Averroism" or "radical Aristotelianism" in the universities. In response to these perceived evils, Thomas wrote two works, one of them being De unitate intellectus, contra Averroistas (On the Unity of Intellect, against the Averroists) in which he blasts Averroism as incompatible with Christian doctrine. During his second regency, he finished the second part of the Summa and wrote De virtutibus and De aeternitate mundi, the latter of which dealt with controversial Averroist and Aristotelian beginninglessness of the world.
Disputes with some important Franciscans such as Bonaventure and John Peckham conspired to make his second regency much more difficult and troubled than the first. A year before Thomas re-assumed the regency at the 1266–67 Paris disputations, Franciscan master William of Baglione accused Thomas of encouraging Averroists, calling him the "blind leader of the blind". Thomas called these individuals the murmurantes (Grumblers).
In reality, Thomas was deeply disturbed by the spread of Averroism and was angered when he discovered Siger of Brabant teaching Averroistic interpretations of Aristotle to Parisian students. On 10 December 1270, the Bishop of Paris, Etienne Tempier, issued an edict condemning thirteen Aristotelian and Averroistic propositions as heretical and excommunicating anyone who continued to support them. Many in the ecclesiastical community, the so-called Augustinians, were fearful that this introduction of Aristotelianism and the more extreme Averroism might somehow contaminate the purity of the Christian faith. In what appears to be an attempt to counteract the growing fear of Aristotelian thought, Thomas conducted a series of disputations between 1270 and 1272: De virtutibus in communi (On Virtues in General), De virtutibus cardinalibus (On Cardinal Virtues), De spe (On Hope).
Final days and "straw" (1272–1274)
In 1272 Thomas took leave from the University of Paris when the Dominicans from his home province called upon him to establish a studium generale wherever he liked and staff it as he pleased. He chose to establish the institution in Naples, and moved there to take his post as regent master. He took his time at Naples to work on the third part of the Summa while giving lectures on various religious topics. He also preached to the people of Naples every day in Lent, 1273. These sermons on the commandments, the creed, the Our Father and Hail Mary were very popular.
On one occasion, at 1273 at the Dominican convent of Naples in the chapel of Saint Nicholas, after Matins, Thomas lingered and was seen by the sacristan Domenic of Caserta to be levitating in prayer with tears before an icon of the crucified Christ. Christ said to Thomas, "You have written well of me, Thomas. What reward would you have for your labor?" Thomas responded, "Nothing but you, Lord."  After this exchange something happened, but Thomas never spoke of it or wrote it down.
On 6 December 1273, another mystical experience took place. While he was celebrating Mass, he experienced an unusually long ecstasy. Because of what he saw, he abandoned his routine and refused to dictate to his socius Reginald of Piperno. When Reginald begged him to get back to work, Thomas replied: "Reginald, I cannot, because all that I have written seems like straw to me" (mihi videtur ut palea). As a result, the Summa Theologica would remain uncompleted. What exactly triggered Thomas' change in behavior is believed by Catholics to have been some kind of supernatural experience of God. After taking to his bed, he did recover some strength.
In 1054 the Great Schism had occurred between the Latin Church following the Pope (known as the Catholic Church) in the West, and the Patriarchate of Constantinople in the East (known as the Eastern Orthodox Church). Looking to find a way to reunite the Eastern Orthodox Church and the Catholic Church, Pope Gregory X convened the Second Council of Lyon to be held on 1 May 1274 and summoned Thomas to attend. At the meeting, Thomas' work for Pope Urban IV concerning the Greeks, Contra errores graecorum, was to be presented.
On his way to the Council, riding on a donkey along the Appian Way, he struck his head on the branch of a fallen tree and became seriously ill again. He was then quickly escorted to Monte Cassino to convalesce. After resting for a while, he set out again, but stopped at the Cistercian Fossanova Abbey after again falling ill. The monks nursed him for several days, and as he received his last rites he prayed: "I receive Thee, ransom of my soul. For love of Thee have I studied and kept vigil, toiled, preached and taught...." He died on 7 March 1274 while giving commentary on the Song of Songs.
Claims of levitation
For centuries, there have been recurring claims that Aquinas had the ability to levitate. For example, G. K. Chesterton wrote that, "His experiences included well-attested cases of levitation in ecstasy; and the Blessed Virgin appeared to him, comforting him with the welcome news that he would never be a Bishop."
Condemnation of 1277
In 1277 Étienne Tempier, the same bishop of Paris who had issued the condemnation of 1270, issued another more extensive condemnation. One aim of this condemnation was to clarify that God's absolute power transcended any principles of logic that Aristotle or Averroes 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 Thomistic propositions. Their inclusion badly damaged Thomas' reputation for many years.
In the Divine Comedy, Dante sees the glorified soul of Thomas in the Heaven of the Sun with the other great exemplars of religious wisdom. Dante asserts that Thomas died by poisoning, on the order of Charles of Anjou; Villani (ix. 218) cites this belief, and the Anonimo Fiorentino describes the crime and its motive. But the historian Ludovico Antonio Muratori reproduces the account made by one of Thomas' friends, and this version of the story gives no hint of foul play.
Thomas' theology had begun its rise to prestige. Two centuries later, 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: Ambrose, Augustine of Hippo, Jerome and Gregory. At the Council of Trent, Thomas had the honor of having his Summa theologiae placed on the altar alongside the Bible and the Decretals.
In his encyclical of 4 August 1879, Pope Leo XIII stated that Thomas' 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. Leo XIII also decreed that all Catholic seminaries and universities must teach Thomas' 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.
When the devil's advocate at his canonization process objected that there were no miracles, one of the cardinals answered, "Tot miraculis, quot articulis"—"there are as many miracles (in his life) as articles (in his Summa)". Fifty years after the death of Thomas, on 18 July 1323, Pope John XXII, seated in Avignon, pronounced Thomas a saint.
A monastery at Naples, near the cathedral of St. Januarius, shows a cell in which he supposedly lived. His remains were placed in the Church of the Jacobins in Toulouse on 28 January 1369. Between 1789 and 1974, they were held in the Basilique de Saint-Sernin, Toulouse. In 1974, they were returned to the Church of the Jacobins, where they have remained ever since.
When he was canonized, his feast day was inserted in the General Roman Calendar for celebration on 7 March, the day of his death. Since this date commonly falls within Lent, the 1969 revision of the calendar moved his memorial to 28 January, the date of the translation of his relics to Church of the Jacobins, Toulouse.
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Thomas was a theologian and a Scholastic philosopher. However, he never considered himself a philosopher, and criticized philosophers, whom he saw as pagans, for always "falling short of the true and proper wisdom to be found in Christian revelation." With this in mind, Thomas did have respect for Aristotle, so much so that in the Summa, he often cites Aristotle simply as "the Philosopher." Much of his work bears upon philosophical topics, and in this sense may be characterized as philosophical. Thomas' philosophical thought has exerted enormous influence on subsequent Christian theology, especially that of the Catholic Church, extending to Western philosophy in general. Thomas stands as a vehicle and modifier of Aristotelianism and Neoplatonism. In fact, Thomas modified both Aristotelianism and Neoplatonism by way of heavy reliance on the Pseudo-Dionysius. This source has arguably been assessed not as a communicator of tradition, but as a polemicist, who tried to alter Neo-Platonic tradition in a novel way for the Christian world that would make notions of complicated Divine Hierarchies more of an emphasis than notions of direct relationship with the figure of Christ as Mediator. Indeed, a number of Catholic sources contend that Thomas was influenced more by this concoction than any other source, including Aristotle.
Commentaries on Aristotle
Thomas wrote several important commentaries on Aristotle's works, including On the Soul, Nicomachean Ethics and Metaphysics. His work is associated with William of Moerbeke's translations of Aristotle from Greek into Latin.
Thomas believed "that for the knowledge of any truth whatsoever man needs divine help, that the intellect may be moved by God to its act." However, he believed that human beings have the natural capacity to know many things without special divine revelation, even though such revelation occurs from time to time, "especially in regard to such (truths) as pertain to faith." But this is the light that is given to man by God according to man's nature: "Now every form bestowed on created things by God has power for a determined act[uality], which it can bring about in proportion to its own proper endowment; and beyond which it is powerless, except by a superadded form, as water can only heat when heated by the fire. And thus the human understanding has a form, viz. intelligible light, which of itself is sufficient for knowing certain intelligible things, viz. those we can come to know through the senses."
Virtue denotes a certain perfection of a power. Now a thing's perfection is considered chiefly in regard to its end. But the end of power is act. Wherefore power is said to be perfect, according as it is determinate to its act.
According to Aquinas "…all acts of virtue are prescribed by the natural law: since each one's reason naturally dictates to him to act virtuously. But if we speak of virtuous acts, considered in themselves, i.e., in their proper species, thus not all virtuous acts are prescribed by the natural law: for many things are done virtuously, to which nature does not incline at first; but that, through the inquiry of reason, have been found by men to be conductive to well living." Therefore, we must determine if we are speaking of virtuous acts as under the aspect of virtuous or as an act in its species.
Thomas defined the four cardinal virtues as prudence, temperance, justice, and fortitude. The cardinal virtues are natural and revealed in nature, and they are binding on everyone. There are, however, three theological virtues: faith, hope, and charity. Aquinas also describes the virtues as imperfect (incomplete) and perfect (complete) virtues. A perfect virtue is any virtue with charity, charity completes a cardinal virtue. A non-Christian can display courage, but it would be courage with temperance. A Christian would display courage with charity. These are somewhat supernatural and are distinct from other virtues in their object, namely, God:
Now the object of the theological virtues is God Himself, Who is the last end of all, as surpassing the knowledge of our reason. On the other hand, the object of the intellectual and moral virtues is something comprehensible to human reason. Wherefore the theological virtues are specifically distinct from the moral and intellectual virtues.
Thomas Aquinas wrote "Greed is a sin against God, just as all mortal sins, in as much as man condemns things eternal for the sake of temporal things."
Furthermore, Thomas distinguished four kinds of law: eternal, natural, human, and divine. Eternal law is the decree of God that governs all creation. It is, "That Law which is the Supreme Reason cannot be understood to be otherwise than unchangeable and eternal." Natural law is the human "participation" in the eternal law and is discovered by reason. Natural law is based on "first principles":
. . . this is the first precept of the law, that good is to be done and promoted, and evil is to be avoided. All other precepts of the natural law are based on this . . .
Whether the natural law contains several precepts, or one only is explained by Aquinas, "All the inclinations of any parts whatsoever of human nature, e.g., of the concupiscible and irascible parts, in so far as they are ruled by reason, belong to the natural law, and are reduced to one first precept, as stated above: so that the precepts of the natural law are many in themselves, but are based on one common foundation."
The desires to live and to procreate are counted by Thomas among those basic (natural) human values on which all human values are based. According to Thomas, all human tendencies are geared towards real human goods. In this case, the human nature in question is marriage, the total gift of oneself to another that ensures a family for children and a future for mankind. To clarify for Christian believers, Thomas defined love as "to will the good of another."
Concerning the Human Law, Aquinas concludes, "...that just as, in the speculative reason, from naturally known indemonstrable principles, we draw the conclusions of the various sciences, the knowledge of which is not imparted to us by nature, but acquired by the efforts of reason, so to it is from the precepts of the natural law, as from general and indemonstrable principles, that human reason needs to proceed to the more particular determination of certain matters. These particular determinations, devised by human reason, are called human laws, provided the other essential conditions of law be observed...." Human law is positive law: the natural law applied by governments to societies.
Natural and human law is not adequate alone. The need for human behavior to be directed made it necessary to have Divine law. Divine law is the specially revealed law in the scriptures. Aquinas quotes, "The Apostle says (Hebrews 7.12): The priesthood being translated, it is necessary that a translation also be made of the law. But the priesthood is twofold, as stated in the same passage, viz, the levitical priesthood, and the priesthood of Christ. Therefore the Divine law is twofold, namely, the Old Law and the New Law." 
Thomas Aquinas, refers to animals as dumb and that the natural order has declared animals for man's use. Thomas denied that human beings have any duty of charity to animals because they are not persons. Otherwise, it would be unlawful to kill them for food. But humans should still be charitable to them, for "cruel habits might carry over into our treatment of human beings."
Thomas contributed to economic thought as an aspect of ethics and justice. He dealt with the concept of a just price, normally its market price or a regulated price sufficient to cover seller costs of production. He argued it was immoral for sellers to raise their prices simply because buyers were in pressing need for a product.
Aquinas' theory of political order became highly influential. He sees man as a social being that lives in a community and interacts with its other members. That leads, among other things, to the division of labour.
Thomas thinks that monarchy is the best form of government, because a monarch does not have to form compromises with other persons. Moreover, according to Thomas, oligarchy degenerates more easily into tyranny than monarchy. To prevent a king from becoming a tyrant, his political powers must be curbed. Unless an agreement of all persons involved can be reached, a tyrant must be tolerated, as otherwise the political situation could deteriorate into anarchy, which would be even worse than tyranny.
The kings are God's representatives in their territories. But the church, represented by the popes, is above the kings in matters of doctrine and morality. As a consequence, the kings and other worldly rulers are obliged to adapt their laws to the Catholic church's doctrines and ethics. For example, the worldly authorities have to execute persons whom the church has sentenced to death for heresy and they have to fight and subdue groups of heretics such as the Albigenses and Waldensians to restore the unity of the church.
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Aquinas maintains that a human is a single material substance. He understands the soul as the form of the body, which makes a human being the composite of the two. Thus, only living, form-matter composites can truly be called human; dead bodies are "human" only analogously. One actually existing substance comes from body and soul. A human is a single material substance, but still should be understood as having an immaterial soul, which continues after bodily death.
In his Summa theologiae Aquinas clearly states his position on the nature of the soul; defining it as "the first principle of life." The soul is not corporeal, or a body; it is the act of a body. Because the intellect is incorporeal, it does not use the bodily organs, as "the operation of anything follows the mode of its being."
According to Thomas the soul is not matter, not even incorporeal or spiritual matter. If it were, it would not be able to understand universals, which are immaterial. A receiver receives things according to the receiver's own nature, so for soul (receiver) to understand (receive) universals, it must have the same nature as universals. Yet, any substance that understands universals may not be a matter-form composite. So, humans have rational souls, which are abstract forms independent of the body. But a human being is one existing, single material substance that comes from body and soul: that is what Thomas means when he writes that "something one in nature can be formed from an intellectual substance and a body", and "a thing one in nature does not result from two permanent entities unless one has the character of substantial form and the other of matter."
The soul is a "substantial form"; it is a part of a substance, but it is not a substance by itself. Nevertheless, the soul exists separately from the body, and continues, after death, in many of the capacities we think of as human. Substantial form is what makes a thing a member of the species to which it belongs, and substantial form is also the structure or configuration that provides the object with the abilities that make the object what it is. For humans, those abilities are those of the rational animal.
These distinctions can be better understood in the light of Aquinas' understanding of matter and form, a hylomorphic ("matter/form") theory derived from Aristotle. In any given substance, matter and form are necessarily united, and each is a necessary aspect of that substance. However, they are conceptually separable. Matter represents what is changeable about the substance – what is potentially something else. For example, bronze matter is potentially a statue, or also potentially a cymbal. Matter must be understood as the matter of something. In contrast, form is what determines some particular chunk of matter to be a specific substance and no other. When Aquinas says that the human body is only partly composed of matter, he means the material body is only potentially a human being. The soul is what actualizes that potential into an existing human being. Consequently, the fact that a human body is live human tissue entails that a human soul is wholly present in each part of the human.
Walter Freeman proposes that Thomism is the philosophical system explaining cognition that is most compatible with neurodynamics, in a 2008 article in the journal Mind and Matter entitled "Nonlinear Brain Dynamics and Intention According to Aquinas."
Thomas viewed theology, or the sacred doctrine, as a science, the raw material data of which consists of written scripture and the tradition of the Catholic Church. These sources of data were produced by the self-revelation of God to individuals and groups of people throughout history. Faith and reason, while distinct but related, are the two primary tools for processing the data of theology. Thomas believed both were necessary—or, rather, that the confluence of both was necessary—for one to obtain true knowledge of God. Thomas blended Greek philosophy and Christian doctrine by suggesting that rational thinking and the study of nature, like revelation, were valid ways to understand truths pertaining to God. According to Thomas, God reveals himself through nature, so to study nature is to study God. The ultimate goals of theology, in Thomas' mind, are to use reason to grasp the truth about God and to experience salvation through that truth.
Thomas believed that truth is known through reason (natural revelation) and faith (supernatural revelation). Supernatural revelation has its origin in the inspiration of the Holy Spirit and is made available through the teaching of the prophets, summed up in Holy Scripture, and transmitted by the Magisterium, the sum of which is called "Tradition". Natural revelation is the truth available to all people through their human nature and powers of reason. For example, he felt this applied to rational ways to know the existence of God.
Though one may deduce the existence of God and his Attributes (Unity, Truth, Goodness, Power, Knowledge) through reason, certain specifics may be known only through the special revelation of God through Jesus Christ. The major theological components of Christianity, such as the Trinity, the Incarnation, and charity are revealed in the teachings of the Church and the Scriptures and may not otherwise be deduced.
Preserving nature within grace
Revealed knowledge does not negate the truth and the completeness of human science as human, it further establishes them. First, it grants that the same things can be treated from two different perspectives without one canceling the other; thus there can be two sciences of God. Second, it provides the basis for the two sciences: one functions through the power of the light of natural reason, the other through the light of divine revelation. Moreover, they can, at least to some extent, keep out of each other's way because they differ "according to genus". Sacred doctrine is a fundamentally different kind of thing from theology, which is part of philosophy (ST I. 1.1 ad 2).
Faith and reason complement rather than contradict each other, each giving different views of the same truth.
As a Catholic Thomas believed that God is the "maker of heaven and earth, of all that is visible and invisible." Like Aristotle, Thomas posited that life could form from non-living material or plant life, a theory of ongoing abiogenesis known as spontaneous generation:
Since the generation of one thing is the corruption of another, it was not incompatible with the first formation of things, that from the corruption of the less perfect the more perfect should be generated. Hence animals generated from the corruption of inanimate things, or of plants, may have been generated then.
Additionally Thomas considered Empedocles's theory that various mutated species emerged at the dawn of Creation. Thomas reasoned that these species were generated through mutations in animal sperm, and argued that they were not unintended by nature; rather, such species were simply not intended for perpetual existence. That discussion is found in his commentary on Aristotle's Physics:
The same thing is true of those substances Empedocles said were produced at the beginning of the world, such as the ‘ox-progeny’, i.e., half ox and half man. For if such things were not able to arrive at some end and final state of nature so that they would be preserved in existence, this was not because nature did not intend this [a final state], but because they were not capable of being preserved. For they were not generated according to nature, but by the corruption of some natural principle, as it now also happens that some monstrous offspring are generated because of the corruption of seed.
Augustine of Hippo agreed strongly with the conventional wisdom of his time, that Christians should be pacifists philosophically, but that they should use defense as a means of preserving peace in the long run. For example, he routinely argued that pacifism did not prevent the defence of innocents. In essence, the pursuit of peace might require fighting to preserve it in the long-term. Such a war must not be preemptive, but defensive, to restore peace.
Clearly, some special characteristics sets apart "war" from "schism", "brawling", and "sedition." While it would be contradictory to speak of a "just schism", a "just brawling" or a "just sedition" (the three terms denote sin and sin only) "war" alone permits sub classification into good and bad kinds. Curiously, however, Augustine does not work up a terminological contrast between "just" and "unjust" war.  Thomas Aquinas, centuries later, used the authority of Augustine's arguments in an attempt to define the conditions under which a war could be just. He laid these out in his historic work, Summa Theologica:
- First, war must occur for a good and just purpose rather than the pursuit of wealth or power.
- Second, just war must be waged by a properly instituted authority such as the state.
- Third, peace must be a central motive even in the midst of violence.
School of Salamanca
The School of Salamanca expanded Aquinas' understanding of natural law and just war. Given that war is one of the worst evils suffered by mankind, the adherents of the School reasoned that it ought to be resorted to only when it was necessary to prevent an even greater evil. A diplomatic agreement is preferable, even for the more powerful party, before a war is started. Examples of "just war" are:
- In self-defense, as long as there is a reasonable possibility of success. If failure is a foregone conclusion, then it is just a wasteful spilling of blood.
- Preventive war against a tyrant who is about to attack.
- War to punish a guilty enemy.
A war is not legitimate or illegitimate simply based on its original motivation: it must comply with a series of additional requirements:
- The response must be commensurate with the evil; more violence than is strictly necessary would be unjust.
- Governing authorities declare war, but their decision is not sufficient cause to begin a war. If the people oppose a war, then it is illegitimate. The people have a right to depose a government that is waging, or is about to wage, an unjust war.
- Once war has begun, there remain moral limits to action. For example, one may not attack innocents or kill hostages.
- The belligerents must exhaust all options for dialogue and negotiation before undertaking a war; war is only legitimate as a last resort.
Nature of God
Thomas believed that the existence of God is self-evident in itself, but not to us. "Therefore I say that this proposition, "God exists", of itself is self-evident, for the predicate is the same as the subject.... Now because we do not know the essence of God, the proposition is not self-evident to us; but needs to be demonstrated by things that are more known to us, though less known in their nature—namely, by effects."
Thomas believed that the existence of God can be demonstrated. Briefly in the Summa theologiae and more extensively in the Summa contra Gentiles, he considered in great detail five arguments for the existence of God, widely known as the quinque viae (Five Ways).
- Motion: Some things undoubtedly move, though cannot cause their own motion. Since, as Thomas believed, there can be no infinite chain of causes of motion, there must be a First Mover not moved by anything else, and this is what everyone understands by God.
- Causation: As in the case of motion, nothing can cause itself, and an infinite chain of causation is impossible, so there must be a First Cause, called God.
- Existence of necessary and the unnecessary: Our experience includes things certainly existing but apparently unnecessary. Not everything can be unnecessary, for then once there was nothing and there would still be nothing. Therefore, we are compelled to suppose something that exists necessarily, having this necessity only from itself; in fact itself the cause for other things to exist.
- Gradation: If we can notice a gradation in things in the sense that some things are more hot, good, etc., there must be a superlative that is the truest and noblest thing, and so most fully existing.
- Ordered tendencies of nature: A direction of actions to an end is noticed in all bodies following natural laws. Anything without awareness tends to a goal under the guidance of one who is aware. 
Concerning the nature of God, Thomas felt the best approach, commonly called the via negativa, is to consider what God is not. This led him to propose five statements about the divine qualities:
- God is simple, without composition of parts, such as body and soul, or matter and form.
- God is perfect, lacking nothing. That is, God is distinguished from other beings on account of God's complete actuality. Thomas defined God as the ‘Ipse subsistens,’ subsisting act of being.
- God is infinite. That is, God is not finite in the ways that created beings are physically, intellectually, and emotionally limited. This infinity is to be distinguished from infinity of size and infinity of number.
- God is immutable, incapable of change on the levels of God's essence and character.
- God is one, without diversification within God's self. The unity of God is such that God's essence is the same as God's existence. In Thomas' words, "in itself the proposition 'God exists' is necessarily true, for in it subject and predicate are the same."
Nature of Sin
Following St. Augustine of Hippo, Thomas defines sin as "a word, deed, or desire, contrary to the eternal law." It is important to note the analogous nature of law in Thomas' legal philosophy. Natural law is an instance or instantiation of eternal law. Because natural law is what human beings determine according to their own nature (as rational beings), disobeying reason is disobeying natural law and eternal law. Thus eternal law is logically prior to reception of either "natural law" (that determined by reason) or "divine law" (that found in the Old and New Testaments). In other words, God's will extends to both reason and revelation. Sin is abrogating either one's own reason, on the one hand, or revelation on the other, and is synonymous with "evil" (privation of good, or privatio boni). Thomas, like all Scholastics, generally argued that the findings of reason and data of revelation cannot conflict, so both are a guide to God's will for human beings.
Nature of the Trinity
Thomas argued that God, while perfectly united, also is perfectly described by Three Interrelated Persons. These three persons (Father, Son, and Holy Spirit) are constituted by their relations within the essence of God. Thomas wrote that the term "Trinity" "does not mean the relations themselves of the Persons, but rather the number of persons related to each other; and hence it is that the word in itself does not express regard to another." The Father generates the Son (or the Word) by the relation of self-awareness. This eternal generation then produces an eternal Spirit "who enjoys the divine nature as the Love of God, the Love of the Father for the Word."
This Trinity exists independently from the world. It transcends the created world, but the Trinity also decided to give grace to human beings. This takes place through the Incarnation of the Word in the person of Jesus Christ and through the indwelling of the Holy Spirit within those who have experienced salvation by God; according to Aidan Nichols.
Prima causa (first cause)
Thomas' five proofs for the existence of God take some of Aristotle's assertions concerning principles of being. For God as prima causa ("first cause") comes from Aristotle's concept of the unmoved mover and asserts that God is the ultimate cause of all things.
Nature of Jesus Christ
In the Summa Theologica Thomas begins his discussion of Jesus Christ by recounting the biblical story of Adam and Eve and by describing the negative effects of original sin. The purpose of Christ's Incarnation was to restore human nature by removing the contamination of sin, which humans cannot do by themselves. "Divine Wisdom judged it fitting that God should become man, so that thus one and the same person would be able both to restore man and to offer satisfaction." Thomas argued in favor of the satisfaction view of atonement; that is, that Jesus Christ died "to satisfy for the whole human race, which was sentenced to die on account of sin."
Thomas argued against several specific contemporary and historical theologians who held differing views about Christ. In response to Photinus, Thomas stated that Jesus was truly divine and not simply a human being. Against Nestorius, who suggested that Son of God was merely conjoined to the man Christ, Thomas argued that the fullness of God was an integral part of Christ's existence. However, countering Apollinaris's views, Thomas held that Christ had a truly human (rational) soul, as well. This produced a duality of natures in Christ. Thomas argued against Eutyches that this duality persisted after the Incarnation. Thomas stated that these two natures existed simultaneously yet distinguishably in one real human body, unlike the teachings of Manichaeus and Valentinus.
With respect to Saint Paul's assertion that Christ, "though he was in the form of God... emptied himself" (Philippians 2:6–7) in becoming human, Thomas offered an articulation of divine kenosis that has informed much subsequent Catholic Christology. Following the Council of Nicaea, Saint Augustine of Hippo, as well as the assertions of Scripture, Aquinas held the doctrine of divine immutability. Hence, in becoming human, there could be no change in the divine person of Christ. For Thomas “The mystery of Incarnation was not completed through God being changed in any way from the state in which He had been from eternity, but through His having united Himself to the creature in a new way, or rather through having united it to Himself.” Similarly, Thomas explained that Christ "emptied Himself, not by putting off His divine nature, but by assuming a human nature." For Thomas, "the divine nature is sufficiently full, because every perfection of goodness is there. But human nature and the soul are not full, but capable of fulness, because it was made as a slate not written upon. Therefore, human nature is empty." Thus, when Paul indicates that Christ "emptied himself" this is to be understood in light of his assumption of a human nature.
In short "Christ had a real body of the same nature of ours, a true rational soul, and, together with these, perfect Deity." Thus, there is both unity (in his one hypostasis) and composition (in his two natures, human and Divine) in Christ.
I answer that, The Person or hypostasis of Christ may be viewed in two ways. First as it is in itself, and thus it is altogether simple, even as the Nature of the Word. Secondly, in the aspect of person or hypostasis to which it belongs to subsist in a nature; and thus the Person of Christ subsists in two natures. Hence though there is one subsisting being in Him, yet there are different aspects of subsistence, and hence He is said to be a composite person, insomuch as one being subsists in two.
Goal of human life
Thomas identified the goal of human existence as union and eternal fellowship with God. This goal is achieved through the beatific vision, in which a person experiences perfect, unending happiness by seeing the essence of God. The vision occurs after death as a gift from God to those who in life experienced salvation and redemption through Christ.
The goal of union with God has implications for the individual's life on earth. Thomas stated that an individual's will must be ordered toward right things, such as charity, peace, and holiness. He saw this orientation as also the way to happiness. Indeed, Thomas ordered his treatment of the moral life around the idea of happiness. The relationship between will and goal is antecedent in nature "because rectitude of the will consists in being duly ordered to the last end [that is, the beatific vision]." Those who truly seek to understand and see God will necessarily love what God loves. Such love requires morality and bears fruit in everyday human choices.
Treatment of heretics
Thomas Aquinas belonged to the Dominican Order (formally Ordo Praedicatorum, the Order of Preachers) who began as an order dedicated to the conversion of the Albigensians and other heterodox factions, at first by peaceful means; later the Albigensians were dealt with by means of the Albigensian Crusade. In the Summa theologiae, he wrote:
With regard to heretics two points must be observed: one, on their own side; the other, on the side of the Church. On their own side there is the sin, whereby they deserve not only to be separated from the Church by excommunication, but also to be severed from the world by death. For it is a much graver matter to corrupt the faith that quickens the soul, than to forge money, which supports temporal life. Wherefore if forgers of money and other evil-doers are forthwith condemned to death by the secular authority, much more reason is there for heretics, as soon as they are convicted of heresy, to be not only excommunicated but even put to death. On the part of the Church, however, there is mercy, which looks to the conversion of the wanderer, wherefore she condemns not at once, but "after the first and second admonition", as the Apostle directs: after that, if he is yet stubborn, the Church no longer hoping for his conversion, looks to the salvation of others, by excommunicating him and separating him from the Church, and furthermore delivers him to the secular tribunal to be exterminated thereby from the world by death.(Summa, II–II, Q.11, art.3.)
Heresy was a capital offense against the secular law of most European countries of the 13th century, which had a limited prison capacity. Kings and emperors, even those at war with the papacy, listed heresy first among the crimes against the state. Kings claimed power from God according to the Christian faith. Often enough, especially in that age of papal claims to universal worldly power, the rulers' power was tangibly and visibly legitimated directly through coronation by the pope.
Simple theft, forgery, fraud, and other such crimes were also capital offenses; Thomas' point seems to be that the gravity of this offense, which touches not only the material goods but also the spiritual goods of others, is at least the same as forgery. Thomas' suggestion specifically demands that heretics be handed to a "secular tribunal" rather than magisterial authority. That Thomas specifically says that heretics "deserve... death" is related to his theology, according to which all sinners have no intrinsic right to life ("For the wages of sin is death; but the free gift of God is eternal life in Christ Jesus our Lord"). Nevertheless, his point is clear: heretics should be executed by the state. He elaborates on his opinion regarding heresy in the next article, when he says:
In God's tribunal, those who return are always received, because God is a searcher of hearts, and knows those who return in sincerity. But the Church cannot imitate God in this, for she presumes that those who relapse after being once received, are not sincere in their return; hence she does not debar them from the way of salvation, but neither does she protect them from the sentence of death. (Summa, op. cit., art.4.)
Thoughts on afterlife and resurrection
A grasp of Aquinas' psychology is essential for understanding his beliefs around the afterlife and resurrection. Thomas, following Church doctrine, accepts that the soul continues to exist after the death of the body. Because he accepts that the soul is the form of the body, then he also must believe that the human being, like all material things, is form-matter composite. Substantial form (the human soul) configures prime matter (the physical body) and is the form by which a material composite belongs to that species it does; in the case of human beings, that species is rational animal. So, a human being is a matter-form composite that is organized to be a rational animal. Matter cannot exist without being configured by form, but form can exist without matter—which allows for the separation of soul from body. Aquinas says that the soul shares in the material and spiritual worlds, and so has some features of matter and other, immaterial, features (such as access to universals). The human soul is different from other material and spiritual things; it is created by God, but also only comes into existence in the material body.
Human beings are material, but the human person can survive the death of the body through continued existence of the soul, which persists. The human soul straddles the spiritual and material worlds, and is both a configured subsistent form as well as a configurer of matter into that of a living, bodily human. Because it is spiritual, the human soul does not depend on matter and may exist separately. Because the human being is a soul-matter composite, the body has a part in what it is to be human. Perfected human nature consists in the human dual nature, embodied and intellecting.
Resurrection appears to require dualism, which Thomas rejects. Yet, Aquinas believes the soul persists after the death and corruption of the body, and is capable of existence, separated from the body between the time of death and the resurrection. Aquinas believes in a different sort of dualism, one guided by Christian scripture. Aquinas knows that human beings are essentially physical, but physicality has a spirit capable of returning to God after life. For Aquinas, the rewards and punishment of the afterlife are not only spiritual. Because of this, resurrection is an important part of his philosophy on the soul. The human is fulfilled and complete in the body, so the hereafter must take place with souls enmattered in resurrected bodies. In addition to spiritual reward, humans can expect to enjoy material and physical blessings. Because Aquinas' soul requires a body for its actions, during the afterlife, the soul will also be punished or rewarded in corporeal existence.
Aquinas states clearly his stance on resurrection, and uses it to back up his philosophy of justice; that is, the promise of resurrection compensates Christians who suffered in this world through a heavenly union with the divine. He says, "If there is no resurrection of the dead, it follows that there is no good for human beings other than in this life." Resurrection provides the impetus for people on earth to give up pleasures in this life. Thomas believes the human who prepared for the afterlife both morally and intellectually will be rewarded more greatly; however, all reward is through the grace of God. Aquinas insists beatitude will be conferred according to merit, and will render the person better able to conceive the divine. Aquinas accordingly believes punishment is directly related to earthly, living preparation and activity as well. Aquinas' account of the soul focuses on epistemology and metaphysics, and because of this he believes it gives a clear account of the immaterial nature of the soul. Aquinas conservatively guards Christian doctrine, and thus maintains physical and spiritual reward and punishment after death. By accepting the essentiality of both body and soul, he allows for a heaven and hell described in scripture and church dogma.
Many modern ethicists both within and outside the Catholic Church (notably Philippa Foot and Alasdair MacIntyre) have recently commented on the possible use of Thomas' virtue ethics as a way of avoiding utilitarianism or Kantian "sense of duty" (called deontology). Through the work of twentieth-century philosophers such as Elizabeth Anscombe (especially in her book Intention), Thomas' principle of double effect specifically and his theory of intentional activity generally have been influential.
In recent years the cognitive neuroscientist Walter Freeman proposes that Thomism is the philosophical system explaining cognition that is most compatible with neurodynamics, in a 2008 article in the journal Mind and Matter entitled "Nonlinear Brain Dynamics and Intention According to Aquinas."
Henry Adams' Mont Saint Michel and Chartres ends with a culminating chapter on Aquinas, in which Adams calls Aquinas an "artist" and constructs an extensive analogy between the design of Aquinas' "Church Intellectual" and that of the gothic cathedrals of that period. Erwin Panofsky later would echo these views in Gothic Architecture and Scholasticism (1951).
Thomas' aesthetic theories, especially the concept of claritas, deeply influenced the literary practice of modernist writer James Joyce, who used to extol Thomas as being second only to Aristotle among Western philosophers. Joyce refers to Aquinas' doctrines in Elementa philosophiae ad mentem D. Thomae Aquinatis doctoris angelici (1898) of Girolamo Maria Mancini, professor of theology at the Collegium Divi Thomae de Urbe. For example, Mancini's Elementa is referred to in Joyce's Portrait of the Artist as a Young Man.
The influence of Thomas' aesthetics also can be found in the works of the Italian semiotician Umberto Eco, who wrote an essay on aesthetic ideas in Thomas (published in 1956 and republished in 1988 in a revised edition).
Criticism of Aquinas as philosopher
Bertrand Russell criticized Aquinas' philosophy stating that,
He does not, like the Platonic Socrates, set out to follow wherever the argument may lead. He is not engaged in an inquiry, 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.
This critique is illustrated on the following examples: According to Russell, Aquinas advocates the indissolubility of marriage "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." Even though modern approaches to education do not support these views, "No follower of Saint Thomas would, on that account, cease to believe in lifelong monogamy, because the real grounds of belief are not those which are alleged." It may be countered that the treatment of matrimony in the Summa Theologica is in the Supplements volume, which was not written by Aquinas. Moreover, as noted above, Aquinas' introduction of arguments and concepts from the pagan Aristotle and Muslim Averroes was controversial within the Catholic Church of his day.
Aquinas' views of God as first cause, cf. quinque viae, "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." Moreover, according to Russell, statements regarding God's essence and existence that are reached within the Aristotelian logic are based on "some kind of syntactical confusion, without which much of the argumentation about God would lose its plausibility."
The first edition of Aquinas' opera omnia, the so-called editio Piana (from Pius V, the Dominican Pope who commissioned it), was produced in 1570 at the studium of the Roman convent at Santa Maria sopra Minerva, the forerunner of the Pontifical University of Saint Thomas Aquinas, Angelicum.
The critical edition of Aquinas' works is the ongoing edition commissioned by Pope Leo XIII (1882-1903), the so-called Leonine Edition. Most of his major works have now been edited, the Summa Theologiae in nine volumes during 1888–1906, the Summa contra Gentiles in three volumes during 1918–1930.
- Adoro te devote
- Aquinas Institute
- Aquinas School in San Juan City, Philippines
- Aquinas University in Legazpi City, Philippines
- Bartholomew of Lucca, Thomas' friend and confessor
- Christian mysticism
- High Middle Ages
- International Council of Universities of Saint Thomas Aquinas
- Lauda Sion
- List of institutions named after Thomas Aquinas
- Medieval university
- Pange Lingua Gloriosi Corporis Mysterium
- Pontifical Academy of St. Thomas Aquinas
- Pontifical University of St. Thomas Aquinas (Angelicum)
- Sacris solemniis
- St. Thomas Aquinas College
- School of Salamanca, 16th-century Spanish Thomists
- Statues of Madonna, Saint Dominic and Thomas Aquinas, Charles Bridge
- St. Thomas Aquinas High School (Florida)
- Thomas Aquinas and the Sacraments
- Thought of Thomas Aquinas
- University of Santo Tomas
- University of St. Thomas (Minnesota)
- Verbum Supernum Prodiens
- Saint Thomas Aquinas – CatholicSaints.Info
- A. C. Brown, Jonathan (2014). Misquoting Muhammad: The Challenge and Choices of Interpreting the Prophet's Legacy. Oneworld Publications. p. 12. ISBN 978-1780744209.
Thomas Aquinas admitted relying heavily on Averroes to understand Aristotle.
- Conway, John Placid, O.P., Father (1911). Saint Thomas Aquinas. London.
- Rev. Vaughan, Roger Bede (1871). The Life and Labours of St. Thomas of Aquin: Vol.I. London.
- See Pius XI, Studiorum Ducem 11 (29 June 1923), AAS, XV ("non modo Angelicum, sed etiam Communem seu Universalem Ecclesiae Doctorem"). The title Doctor Communis dates to the fourteenth century; the title Doctor Angelicus dates to the fifteenth century, see Walz, Xenia Thomistica, III, p. 164 n. 4. Tolomeo da Lucca writes in Historia Ecclesiastica (1317): "This man is supreme among modern teachers of philosophy and theology, and indeed in every subject. And such is the common view and opinion, so that nowadays in the University of Paris they call him the Doctor Communis because of the outstanding clarity of his teaching." Historia Eccles. xxiii, c. 9.
- Code of Canon Law, Can. 252, §3 
- Benedict XV Encyclical Fausto appetente die 29 June 1921, AAS 13 (1921), 332; Pius XI Encyclical Studiorum Ducem §11, 29 June 1923, AAS 15 (1923), cf. AAS 17 (1925) 574; Paul VI, 7 March 1964 AAS 56 (1964), 302 (Bouscaren, vol. VI, pp. 786–88).
- Jean-Pierre Torrell, Saint Thomas Aquinas: The Person And His Work, CUA press, 2005, p. 3. Google Book
- Hampden, The Life, p. 14.
- Stump, Aquinas, p. 3.
- Schaff, Philip (1953). Thomas Aquinas, pp. 422–423.
- Davies, Aquinas: An Introduction, pp. 1–2
- Davies, Aquinas: An Introduction, p. 2
- Hampden, The Life, pp. 21–22.
- Grabmann, Martin. Virgil Michel, trans. Thomas Aquinas: His Personality and Thought. (Kessinger Publishing, 2006), pp. 2.
- Collison, Diane, and Kathryn Plant. Fifty Major Philosophers. 2nd ed. New York: Routledge, 2006.
- Hampden, The Life, p. 23.
- Hampden, The Life, p. 24.
- Hampden, The Life, p. 25.
- Hampden, The Life, pp. 27–28.
- Healy, Theologian, p. 2.
- Hampden, The Life, p. 33.
- Stump, Aquinas, p. xvi.
- Davies, The Thought, p. 5.
- Aquinas, Thomas; Richard J. Regan; Brian Davies (2003). On Evil. Oxford University Press US. p. 5. ISBN 0-19-509183-3.
- Stump, Aquinas, p. 4.
- Davies, Aquinas: An Introduction, pp. 3–4.
- Stump, Aquinas, p. xvii.
- Davies, Aquinas: An Introduction, p. 4.
- Healy, Theologian, p. 4.
- Torrell, "Saint Thomas Aquinas", pp. 129-132.
- Fr. Thome de Aquino iniungimus in remissionem peccatorum quod teneat studium Rome, et volumus quod fratribus qui stant secum ad studendum provideatur in necessariis vestimentis a conventibus de quorum predicatione traxerunt originem. Si autem illi studentes inventi fuerint negligentes in studio, damus potestatem fr. Thome quod ad conventus suos possit eos remittere (Acta Capitulorum Provincialium, Provinciae Romanae Ordinis Praedicatorum, 1265, n. 12)http://www.corpusthomisticum.org/a65.html
- Compendium Historiae Ordinis Praedicatorum, A.M. Walz, Herder 1930, 214: "Conventus S. Sabinae de Urbe prae ceteris gloriam singularem ex praesentia fundatoris ordinis et primitivorum fratrum necnon ex residentia Romana magistrorum generalium, si de ea sermo esse potest, habet. In documentis quidem eius nonnisi anno 1222 nomen fit, ait certe iam antea nostris concreditus est. Florebant ibi etiam studia sacra." https://archive.org/stream/MN5081ucmf_3/MN5081ucmf_3_djvu.txt Accessed 4-9-2011.
- Marian Michèle Mulchahey, "First the bow is bent in study": Dominican education before 1350, 1998, p. 278-279. https://books.google.com/books?id=bK9axCYcbFIC&pg=PA279#v=onepage&q&f=false Accessed 6-30-2011
- "Tenuit studium Rome, quasi totam Philosophiam, sive Moralem, sive Naturalem exposuit." Ptolomaei Lucensis historia ecclesiastica nova, xxii, c. 24, in Ferdinand Gregorovius "History of the City of Rome In the Middle Ages", Vol V, part II, 617, note 2. http://www.third-millennium-library.com/PDF/Authors/Gregorovius/history-of-rome-city_5_2.pdf Accessed 6-5-2011. Archived 5 October 2011 at the Wayback Machine.
- Summa theologiae, I, 1, prooemium:"Quia Catholicae veritatis doctor non solum provectos debet instruere, sed ad eum pertinet etiam incipientes erudire, secundum illud apostoli I ad Corinth. III, tanquam parvulis in Christo, lac vobis potum dedi, non escam; propositum nostrae intentionis in hoc opere est, ea quae ad Christianam religionem pertinent, eo modo tradere, secundum quod congruit ad eruditionem incipientium."
- Davies, Aquinas: An Introduction, p. 5.
- http://aquinatis.blogspot.com/2008/05/vida-de-santo-toms-de-aquino.html Accessed 22 June 2011: "A mediados de noviembre abandonó Santo Tomás la ciudad de Viterbo en compañía de fray Reginaldo de Piperno y su discípulo fray Nicolás Brunacci." http://www.brunacci.it/s--tommaso.html Accessed 22 June 2011. http://www.brunacci.it/s--tommaso.html Accessed 22 June 2011: "Per l'acutezza del suo ingegno, dopo aver studiato nella sua provincia, ebbe l'alto onore di accompagnare S. Tommaso a Parigi nel novembre del 1268. Rimase in quello studio fino al 1272 e di là passò a Colonia sotto la disciplina di Alberto Magno."
- http://www.santiebeati.it/dettaglio/92060 Accessed 29 June 2011
- Compendium Historiae Ordinis Praedicatorum, A.M. Walz, Herder 1930, 214: Romanus conventus S. Mariae supra Minervam anno 1255 ex conditionibus parvis crevit. Tunc enim paenitentibus feminis in communi regulariter ibi 1252/53 viventibus ad S. Pancratium migratis fratres Praedicatores domum illam relictam a Summo Pontifice habendam petierunt et impetranint. Qua demum feliciter obtenda capellam hospitio circa annum 1255 adiecerunt. Huc evangelizandi causa fratres e conventu S. Sabinae descendebant. https://archive.org/stream/MN5081ucmf_3/MN5081ucmf_3_djvu.txt Accessed 5-17-2011
- Marian Michèle Mulchahey, "First the bow is bent in study": Dominican education before 1350, 1998, p. 323. https://books.google.com/books?id=bK9axCYcbFIC&pg=PA323 Accessed 5-26-2011
- Stump, Aquinas, pp. 10–11.
- Stump, Aquinas, p. 11.
- Aquinas, Reader, pp. 9–11.
- McInerney, Against the Averroists, p. 10.
- Aquinas, Reader, p. 11.
- James Weisheipl, OP Friar Thomas D'Aquino: His Life, Thought, and Work. (Doubleday, 1974), pp. 319.
- Guilelmus de Tocco, Ystoria sancti Thome de Aquino de Guillaume de Tocco (1323), Pontifical Institute of Mediaeval Studies, 1996, p. 162.
- Catholic Encyclopedia
- "CATHOLIC ENCYCLOPEDIA: St. Thomas Aquinas". www.newadvent.org. Retrieved 2016-08-22.
- Davies, The Thought, p. 9.
- McBride, William Leon (1997). The Development and Meaning of Twentieth-century Existentialism. Taylor and Francis. p. 131. ISBN 0-8153-2491-X.
- McInerny, Ralph and John O'Callaghan, "Saint Thomas Aquinas", The Stanford Encyclopedia of Philosophy (Fall 2008 Edition), Edward N. Zalta (ed.)
- Healy, Theologian, p. 7.
- Nichols, Discovering Aquinas, p. 18.
- Hampden, The Life, p. 46.
- Healy, Theologian, p. 8.
- Aquinas, Reader, p. 12.
- Hampden, The Life, p. 47.
- G. K. Chesterton wrote an Essay on St. Thomas Aquinas, which appeared in The Spectator 27 Feb. 1932.
- Grant, Edward (1996). The Foundations of Modern Science in the Middle Ages: Their Religious, Institutional, and Intellectual Contexts. Cambridge University Press. pp. 81–82. ISBN 0-521-56762-9.
- Kung, Christian Thinkers , pp. 112–114.
- "Parad. x. 99". Divinecomedy.org. Retrieved 2010-01-17.
- "Purg. xx. 69". Divinecomedy.org. Retrieved 2010-01-17.
- "Aquinas, Thomas", Encyclopædia Britannica (1911), pg. 250.
- Brian Mullady, O.P. (2006). "The Angelic Doctor – Thomas Aquinas". Archived from the original on 7 October 2008. Retrieved 2011-06-11.
- Hampden, The Life, p. 54.
- Calendarium Romanum Libreria Editrice Vaticana 1969, p. 86
- Liturgy of the Hours Volume III, Proper of Saints, 28 January.
- Some would not describe Thomas as a philosopher. See, e.g., Mark D. Jordan, "Philosophy in a Summa of Theology", in Rewritten Theology: Aquinas after his Readers (Oxford: Blackwell, 2006) pp. 154–170. 
- Davies, Brian (2004). Aquinas. Continuum International Publishing Group. p. 14.
- "One might ask why it is necessary [in the Pseudo-Dionysian Corpus] to have an ordered hierarchy of angels at all in the Christian tradition, considering that the Bible has no concept of celestial hierarchy....That it was found necessary to invent a system of this nature [in the Pseudo-Dionysisn Corpus] after 500 years is tantamount to denying the efficacy of Christ as mediator altogether." Rosemarie A. Arthur "The Pseudo Dionysius as Polemicist: The Development and Purpose of the Angelic Hierarchy in Sixth Century Syria" London: Ashgate, 2011, pp. 63–64.
- The Catholic source that shows Thomas having been influenced by this concoction more than any other source is discussed in Peter Paul Fuchs "Medieval Confabulations, The Mendicant Controversy, and the Real Templar-Masonic Philosophy" The Association of Masonic Arts http://masonicarts.net/medieval-confabulations-the-mendicant-controversy-and-the-real-templar-masonic-philosophy/
- "Blog Archive " Saint Thomas Aquinas". Saints.SQPN.com. 22 October 1974. Retrieved 2010-01-17.
- "Summa, I-II, Q109a1". Ccel.org. Retrieved 2012-03-25.
- Geisler, p. 727.
- "Summa, Q55a1". Ccel.org. Retrieved 2012-02-02.
- 3. Aquinas
- Summa Theologica, First Part of the Second Part, Question 94 Reply Obj. 2
- Summa Question 94, A.3
- "Summa, Q62a2". Ccel.org. Retrieved 2012-02-02.
- Aquinas Summa Theologica q91 a1
- Pojman, Louis (1995). Ethics: Discovering Right and Wrong. Belmont, California: Wadsworth Publishing Company. ISBN 0-534-56138-1.
- "Summa, Q94a2". Ccel.org. Retrieved 2012-02-02.
- Summa Theologica, Question 94, Second Article Reply Obj.2
- Aquinas, Thomas. "IV In Sententiae. d. 27 q. 1 a.1". Commentary. Retrieved 2011-09-21.
- "St. Thomas Aquinas, STh I-II, 26, 4, corp. art". Newadvent.org. Retrieved 2010-10-30.
- Summa,Q.94, A.3.
- Summa, Q.94, A.5
- Honderich, Ted, ed. (1995). "Animals: Peter Singer". The Oxford Companion to Philosophy. Oxford. pp. 35–36.
- Summa Theologica, second Part of the Second Part, Question 64. Article 1.
- Thomas Aquinas. Summa Theologica. "Of Cheating, Which Is Committed in Buying and Selling." Translated by The Fathers of the English Dominican Province  Retrieved 19 June 2012
- Barry Gordon (1987). "Aquinas, St Thomas (1225–1274)", v. 1, p. 100
- Heinz-Dietrich Wendland (1962): Sklaverei und Christentum. In: Die Religion in Geschichte und Gegenwart, Third Edition, Tübingen (Germany), Vol. VI, col. 103
- Aquinas, Thomas (1920). "Question 75, Article 1". In Literally Translated by the Fathers of the English Dominican Province. Summa Theologiae of St. Thomas Aquinas. Second and Revised Edition.
- Aquinas, Thomas (1920). "Question 75, Article 3". In Literally Translated by the Fathers of the English Dominican Province. Summa Theologiae of St. Thomas Aquinas. Second and Revised Edition.
- Aquinas, Thomas (1975). "5 volumes.". In Translated by Anton C. Pegis et al. Summa Contra Gentiles. Notre Dame, Ind.: U. of Notre Dame Press.
- Hankey, Wayne (2013). The Routledge Companion to Philosophy of Religion (Second ed.). CSU East Bay: Routledge. pp. 134–135. ISBN 978-0-415-78295-1.
- Saint Thomas Aquinas, Summa Theologica, On the Work of the Sixth Day, Reply to Objection 5, Fathers of the English Dominican Province
- Saint Thomas Aquinas, Physica, Book 2, Lecture 14, Fathers of the English Dominican Province
- St. Augustine of Hippo, Crusades-Encyclopedia
- Saint Augustine and the Theory of Just War
- Reichberg, Gregory (June 2010). "Thomas Aquinas between Just War and Pacificism". Journal of Religious Ethics. 38 (2): 219–241. doi:10.1111/j.1467-9795.2010.00427.x.
- The Just War
- Justo L. Gonzalez (1984). The Story of Christianity. HarperSanFrancisco.
- Summa of Theology I, q.2, The Five Ways Philosophers Have Proven God's Existence
- Kreeft, pp. 74–77.
- Kreeft, pp. 86–87.
- See Actus Essendi. See also Online Resources: .
- Kreeft, pp. 97–99.
- Kreeft, p. 105.
- Kreeft, pp. 111–112.
- "Summa, II–I, Q.71, art.6". Newadvent.org. Retrieved 2010-01-17.
- Summa, II–I, Q.75, art.1. "For evil is the absence of the good, which is natural and due to a thing."
- Nichols, Aidan (2002). Discovering Aquinas. Grand Rapids, Michigan: Eerdmans Publishing Company. pp. 173–174.
- Nichols, Aidan (2002). Discovering Aquinas. Grand Rapids, Michigan: Eerdmans Publishing Company. pp. 80–82.
- Aquinas, pp. 228–229.
- "Summa, III, Q.50, art.1". Newadvent.org. Retrieved 2010-01-17.
- Aquinas, pp. 231–239.
- “The Profession of Faith of the 318 Fathers,” First Council of Nicaea – 325 AD, available at http://www.papalencyclicals.net/Councils/ecum01.htm, §2.
- Augustine, Sermo VII, 7.
- For instance, Malachi 3:6 and James 1:17
- ST III.1.1.
- Commentary on Saint Paul’s Letter to the Philippians, available at http://dhspriory.org/thomas/english/SSPhilippians.htm, §2-2.
- Commentary on Saint Paul’s Letter to the Philippians, available at http://dhspriory.org/thomas/english/SSPhilippians.htm, §2-2.</
- Aquinas, pp. 241, 245–249. Emphasis is the author's.
- Weigel, George (2001). The Truth of Catholicism. New York City: Harper Collins. p. 9. ISBN 0-06-621330-4.
- Kreeft, p. 383.
- "Romans 6:23, ASV". Biblegateway.com. Retrieved 2010-01-17.
- Stump, Eleanore (2003). Aquinas, (in the series The Arguments of the Philosophers). London and New York: Routledge. p. 194.
- Stump, Eleanore (2003). Aquinas, (in the series The Arguments of the Philosophers). London and New York: Routledge. p. 200.
- Stump, Eleanore (2003). Aquinas, (in the series The Arguments of the Philosophers). London and New York: Routledge. p. 192.
- Stump, Eleanore (2003). Aquinas, (in the series The Arguments of the Philosophers). London and New York: Routledge. pp. 461, 473.
- The Irish Ecclesiastical Record, Vol V, Year 32, No. 378, June, 1899, p. 570 Accessed 3-7-2013
- A Portrait of the Artist as a Young Man, James Joyce, Wordsworth 1992 edition, Introduction and Notes by Jacqueline Belanger, 2001, p. 136, note 309: "Synopsis Philosophiae ad mentem D. Thomae This appears to be a reference to Elementa Philosophiae ad mentem D. Thomae Aquinatis, a selection of Thomas Aquinas' writings edited and published by G. M. Mancini in 1898. (G)" https://books.google.com/books?id=C_rPXanc_HAC&pg=PA221#v=onepage&q&f=false Accessed 3-6-2013
- (Russell 1967, p. 463) A History of Western Philosophy, Ch. 34, "St. Thomas Aquinas", Allen & Unwin, London; Simon & Schuster, New York 1946, 484-.
- (Russell 1967, p. 462)
- Thomas Aquinas#Condemnation of 1277
- In This Light Which Gives Light: A History of the College of St. Albert the Great, Christopher J. Renzi, p. 42: https://books.google.com/books?id=t8qt63uOg6IC&pg=PA42#v=onepage&q&f=false Accessed 4-24-2011
- Aquinas, Thomas (2000). Mary T. Clark, ed. An Aquinas Reader: Selections from the Writings of Thomas Aquinas. Fordham University Press. ISBN 0-8232-2029-X.
- ——— (2002). Aquinas's Shorter Summa. Manchester, New Hampshire: Sophia Institute Press. ISBN 1-928832-43-1.
- Davies, Brian (1993). The Thought of Thomas Aquinas. Oxford University Press. ISBN 0-19-826753-3.
- ——— (2004). Aquinas: An Introduction. Continuum. ISBN 0-8264-7095-5.
- Geisler, Norman, ed. (1999). Baker Encyclopedia of Christian Apologetics. Grand Rapids, Michigan: Baker Academic.
- Gordon, Barry (2009) , "Aquinas, St Thomas", The New Palgrave: A Dictionary of Economics, 1.
- Hampden, Renn Dickson (1848). "The Life of Thomas Aquinas: A Dissertation of the Scholastic Philosophy of the Middle Ages". Encyclopædia Metropolitana. London: John J. Griffin & Co.
- Healy, Nicholas M. (2003). Thomas Aquinas: Theologian of the Christian Life. Ashgate. ISBN 0-7546-1472-7.
- Kreeft, Peter (1990). Summa of the Summa. Ignatius Press. ISBN 0-89870-300-X.
- Küng, Hans (1994), Great Christian Thinkers, New York: Continuum Books, ISBN 0-8264-0848-6
- McInerny, Ralph M. (1993). Aquinas Against the Averroists: On There Being Only One Intellect. Purdue University Press. ISBN 1-55753-029-7.
- Nichols, Aidan (2003). Discovering Aquinas: An Introduction to His Life, Work, and Influence. Wm. B. Eerdmans. ISBN 0-8028-0514-0.
- Russell, Bertrand (1967), A History of Western Philosophy, Simon & Schuster, ISBN 0-67120158-1
- Schaff, Philip (1953). "Thomas Aquinas". The New Schaff-Herzog Encyclopedia of Religious Knowledge. 126. Grand Rapids, Michigan: Baker Book House. pp. 422–23. Bibcode:1930Natur.126..951G. doi:10.1038/126951c0.
- Stump, Eleonore (2003). Aquinas. Routledge. ISBN 0-415-02960-0.
- This article incorporates text from a publication now in the public domain: Seeburg, Reinhold (1914). "Thomas Aquinas". In Jackson, Samuel Macauley. New Schaff–Herzog Encyclopedia of Religious Knowledge. XI (third ed.). London and New York: Funk and Wagnalls. pp. 422–27.
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Thomas Aquinas". Encyclopædia Britannica (11th ed.). Cambridge University Press.
- Copleston, Frederick (1991). Aquinas: An Introduction to the Life and Work of the Great Medieval Thinker. Penguin Books. ISBN 0-14-013674-6.
- Faitanin, Paulo (2008). A Sabedoria do Amor: iniciação à filosofia de Santo Tomás de Aquino [Love's philosophy: initiation to Saint Thomas Aquinas' philosophy] (in Portuguese). Instituto Aquinate. ISSN 1982-8845.
- ——— (2008). O Ofício do Sábio: o modo de estudar e ensinar segundo Santo Tomás de Aquino [The wise's profession: the way of studying & learning after Saint Thomas Aquinas] (in Portuguese). Instituto Aquinate. ISSN 1982-8845.
- Paterson, Craig & Matthew S. Pugh (eds.), Analytical Thomism: Traditions in Dialogue. Ashgate, 2006. Introduction to Thomism
- Porro, Paquale (2015). Thomas Aquinas: A Historical and Philosophical Profile. Washington, D.C.: Catholic University of America Press. ISBN 978-0-8132-2805-1.
- Schmitz, Kenneth (2007). St. Thomas Aquinas (audiobook). Narrated by Charlton Heston. Ashland, Oregon; Boulder, Colorado: Knowledge Products; Blackstone Audiobooks; NetLibrary. ISBN 0-7861-6932-X. OCLC 78235338.
- Strathern, Paul (1998). Thomas Aquinas in 90 Minutes. Chicago: I.R. Dee. 90 p. ISBN 1-56663-194-7.
- Thomas Aquinas (1952), edd. Walter Farrell, OP, and Martin J. Healy, My Way of Life: Pocket Edition of St. Thomas—The Summa Simplified for Everyone, Brooklyn: Confraternity of the Precious Blood.
- Torrell, Jean-Pierre (2005). Saint Thomas Aquinas (Rev. ed.). Washington, D.C.: Catholic University of America Press. ISBN 978-0-8132-1423-8. OCLC 456104266.
- Wallace, William A (1970). "Thomas Aquinas, Saint". In Gillispie, Charles. Dictionary of Scientific Biography. 1. New York: Scribner & American Council of Learned Societies. pp. 196–200. ISBN 978-0-684-10114-9.
- Weisheipl, James (1974). Friar Thomas D'Aquino: his life, thought, and work (1st ed.). Garden City, New York: Doubleday. ISBN 978-0-385-01299-7.
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- On Being and Essence (De Ente et Essentia)
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- De Magistro (On the teacher q. 11, a.1 of de Veritate)
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