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This article contains a selection of thoughts of Thomas Aquinas on various topics. It is not intended as a complete account of Aquinas's thought. Within Aquinas' thought is included the philosophical school of Thomism.
Aquinas defines distributive justice as follows:
[I]n distributive justice something is given to a private individual, in so far as what belongs to the whole is due to the part, and in a quantity that is proportionate to the importance of the position of that part in respect of the whole. Consequently in distributive justice a person receives all the more of the common goods, according as he holds a more prominent position in the community. This prominence in an aristocratic community is gauged according to virtue, in an oligarchy according to wealth, in a democracy according to liberty, and in various ways according to various forms of community. Hence in distributive justice the mean is observed, not according to equality between thing and thing, but according to proportion between things and persons: in such a way that even as one person surpasses another, so that which is given to one person surpasses that which is allotted to another.
Aquinas asserts that Christians have a duty to distribute with provision to the poorest of society. (See: Gilson, Etienne, "The Christian Philosophy of St. Thomas Aquinas", University of Notre Dame Press, 1994)
The following is a summary of Summa Contra Gentiles, Book 3, Chapter 146, which was written by Aquinas prior to writing the Summa Theologica. St. Thomas was a vocal supporter of the death penalty. This was based on the theory (found in natural moral law), that the state has not only the right, but the duty to protect its citizens from enemies, both from within, and without.
...men who are in authority over others do no wrong when they reward the good and punish the evil.
... for the preservation of concord among men it is necessary that punishments be inflicted on the wicked. Therefore, to punish the wicked is not in itself evil.
Moreover, the common good is better than the particular good of one person. So, the particular good should be removed in order to preserve the common good. But the life of certain pestiferous men is an impediment to the common good which is the concord of human society. Therefore, certain men must be removed by death from the society of men.
Furthermore, just as a physician looks to health as the end in his work, and health consists in the orderly concord of humors, so, too, the ruler of a state intends peace in his work, and peace consists in "the ordered concord of citizens." Now, the physician quite properly and beneficially cuts off a diseased organ if the corruption of the body is threatened because of it. Therefore, the ruler of a state executes pestiferous men justly and sinlessly in order that the peace of the state may not be disrupted.
He based this on I Corinthians 5, 6: "You know that a little leaven corrupts the whole lump of dough?" and I Corinthians 5, 13: "Put away the evil one from among yourselves"; Romans 13,4: "[it is said of earthly power that] he bears not the sword in vain: for he is God's minister, an avenger to execute wrath upon him that does evil"; I Peter 2, 13-14: "Be subjected therefore to every human creature for God's sake: whether to be on the king as excelling, or to governors as sent by him for the punishment of evildoers and for the praise of good."
Aquinas acknowledged these passages could also be interpreted as meaning there should be no use of the death penalty if there was a chance of injuring the innocent. The prohibition "Thou shall not kill", was superseded by Exodus 22,18: "Wrongdoers you shall not suffer to live." The argument that evildoers should be allowed to live in the hope that they might be redeemed was rejected by Aquinas as frivolous. If they would not repent in the face of death, it was unreasonable to assume they would ever repent. "How many people are we to allow to be murdered while waiting for the repentance of the wrongdoer?", he asked, rhetorically. Using the death penalty for revenge, or retribution is a violation of natural moral law.
Many believe the correct interpretation of the commandment to be "Thou shalt not murder." This interpretation allows for Aquinas' belief that the death penalty is an acceptable practice as delivered by those in authority over such things, such as government, which is divinely appointed as to God's will.
Under Pope John Paul II, the Catholic Church came, according to one of two interpretations of Evangelium Vitae ,to advocate incarceration in lieu of the death penalty.
Aquinas advocated the death penalty for obstinate heretics, writing
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 which 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. For Jerome commenting on Galatians 5:9, "A little leaven," says: "Cut off the decayed flesh, expel the mangy sheep from the fold, lest the whole house, the whole paste, the whole body, the whole flock, burn, perish, rot, die. Arius was but one spark in Alexandria, but as that spark was not at once put out, the whole earth was laid waste by its flame." (ST II:II 11:3 corpus)
This position of Aquinas was congruous with the political and religious teaching of the day. The penalty of death for obdurate heretics had been the standard for generations prior to the time of Aquinas. It had been formalized in Canon Law during the Lateran Councils of 1179 and 1215. It was also the standard part of most criminal and civil laws prior to the time of Aquinas. Cathars were executed in Oxford in 1166. Another was burned at the stake in London in 1210. Of course, these, and many others pre-dated Aquinas. Since it was the Church's responsibility to attend to the eternal salvation of souls, heresy could not be tolerated. Heretics were given two chances to recant their views. This is a position which, by modern standards would be considered exceptionally harsh, and has changed and softened since the 13th century. The Church was inexorably intermixed with the secular political structure. This was before the modern concept of separation of church and state had developed. It was also a product of Scholasticism which did not seek to find an equivocal position, but rather to reach a decisive univocal conclusion on matters of religion and philosophy.
As can be seen by reading the article of Michael Novak[ citation needed ], Aquinas' view in this matter is one of the more difficult parts of dealing with Thomism Needless to say, the attitudes of Aquinas were prevalent in his time. This view must be taken in context with the attitude shown by Aquinas in eschewing the forced baptism of the children of heretics, which was recommended by, among others, John Duns Scotus. The heretics Aquinas was referring to were those baptized Catholics who held positions of authority within the Church, and nonetheless persisted in teaching heretical views. It remains one of those passages which must be taken in context of the total message of Thomism. The growth of various heretical positions, leading to the Reformation, made execution of heretics impractical and counterproductive. Excommunication remained the penalty for such Church leaders who taught heresy. Aquinas' view is steeped in the traditions of Roman Law. A review of the legal history prior to the time of Aquinas reveals the nature of recommending execution of heretics. The issue came to a head with the Manichean (Cathari) heresy. Justinian's code confirmed that Manicheanism was a capital crime. It was concluded that other heretics were to be deemed no better. The opinion prevailed in legal circles that human law and divine command demanded the death of the obdurate heretic. It was routinely enforced by both Church and State. In severe cases of religious pestilence, there was a need for a holy war. These prevailing feelings were legislated by the Church in the Lateran Councils of 1179 and 1215.
The impenitent heretic when convicted by the ecclesiastical court for execution.[ citation needed ] Often, there was a plea for the life of the heretic, so as to avoid the appearance of "irregularity" and blood guilt. Frederick II, (1194–1250) incorporated the execution of heretics into his civil and criminal code of the Holy Roman Empire.
Omnipotence is the quality of having unlimited power and potential. Monotheistic religions generally attribute omnipotence only to the deity of their faith. In the monotheistic philosophies of Abrahamic religions, omnipotence is often listed as one of a deity's characteristics among many, including omniscience, omnipresence, and omnibenevolence. The presence of all these properties in a single entity has given rise to considerable theological debate, prominently including the problem of theodicy, the question of why such a deity would permit the manifestation of evil. It is accepted in philosophy and science that omnipotence can never be effectively understood.
Usury is the practice of making unethical or immoral monetary loans that unfairly enrich the lender. The term may be used in a moral sense—condemning, taking advantage of others' misfortunes—or in a legal sense, where an interest rate is charged in excess of the maximum rate that is allowed by law. A loan may be considered usurious because of excessive or abusive interest rates or other factors defined by a nation's laws. Someone who practices usury can be called an usurer, but in contemporary English may be called a loan shark.
The Latin phrase extra Ecclesiam nulla salus means "outside the Church there is no salvation". The 1992 Catechism of the Catholic Church explained this as "all salvation comes from Christ the Head through the Church which is His Body."
Thomism is the philosophical school that arose as a legacy of the work and thought of Thomas Aquinas (1225–1274), philosopher, theologian, and Doctor of the Church. In philosophy, Aquinas' disputed questions and commentaries on Aristotle are perhaps his best-known works.
Aseity is the property by which a being exists in and of itself, from itself, or exists as so-and-such of and from itself. The word is often used to refer to the Christian belief that God contains within himself the cause of himself, is the first cause, or rather is simply uncaused, though many Jewish and Muslim theologians have also believed God to be independent in this way. Notions of aseity as the highest principle go back at least to Plato and have been in wide circulation since Augustine, though the use of the word 'aseity' began only in the Middle Ages.
Thomas Cajetan, also known as Gaetanus, commonly Tommaso de Vio or Thomas de Vio, was an Italian philosopher, theologian, cardinal and the Master of the Order of Preachers 1508-18. He was a leading theologian of his day who is now best known as the spokesman for Catholic opposition to the teachings of Martin Luther and the Protestant Reformation while he was the Pope's Legate in Augsburg, and perhaps also among Catholics for his extensive commentary on the Summa Theologica of Thomas Aquinas.
Peter John Kreeft is a professor of philosophy at Boston College and The King's College. A convert to Roman Catholicism, he is the author of over eighty books on Christian philosophy, theology and apologetics. He also formulated, together with Ronald K. Tacelli, "Twenty Arguments for the Existence of God".
The satisfaction theory of atonement is a theory in Catholic theology which holds the Jesus Christ redeemed humanity through making satisfaction for humankind's disobedience through his own supererogatory obedience. The theory draws primarily from the works of Anselm of Canterbury, specifically his Cur Deus Homo. It has been traditionally taught in the Roman Catholic tradition of Western Christianity. Theologically and historically, the word "satisfaction" does not mean gratification as in common usage, but rather "to make restitution": making an offering the value of which redeems the injury or insult which was inflicted on the offended party. Since one of God's characteristics is justice, affronts to that justice must be atoned for. It is thus connected with the legal concept of balancing out an injustice.
The Summa Theologiae, as the best-known work of Thomas Aquinas, is a compendium of all of the main theological teachings of the Catholic Church, intended to be an instructional guide for theology students, including seminarians and the literate laity. Presenting the reasoning for almost all points of Christian theology in the West, topics of the Summa follow the following cycle: God; Creation, Man; Man's purpose; Christ; the Sacraments; and back to God.
Aeterni Patris was an encyclical issued by Pope Leo XIII in August 1879,. It was subtitled "On the Restoration of Christian Philosophy in Catholic Schools in the Spirit of the Angelic Doctor, St. Thomas Aquinas". The aim of the encyclical was to advance the revival of Scholastic philosophy.
The Quinque viæ are five logical arguments for the existence of God summarized by the 13th-century Catholic philosopher and theologian St. Thomas Aquinas in his book Summa Theologica. They are:
Thomistic sacramental theology is St. Thomas Aquinas's theology of the sacraments of the Catholic Church. It can be found through his writings in the Summa contra Gentiles and in the Summa Theologiæ. As can be seen, Aquinas relied heavily on Scriptural passages, as well as the writings of various Church Fathers. St. Augustine says : "The visible sacrifice is the sacrament. This is the sacred sign of the invisible sacrifice. A thing is called a sacrament, either by having a certain hidden sanctity, and in this sense a sacrament is a sacred secret; or from having some relationship to this sanctity. A sacrament is a sign. Moreover, it is a sacred sign. Divine Wisdom provides for each thing according to its mode. Wisdom 7,1 : "she... ordered all things sweetly"; and from Matthew 25,15: "[she] gave to everyone according to his proper ability." It is a part of human nature to acquire knowledge of the intelligible from the sensible. A sign is the way one obtains knowledge of something else. The sacraments are the signs by which humans gain knowledge of spiritual and intelligible goods. Ephesians 5, 25-26: "Christ loved the Church, and delivered Himself up for it; that He might sanctify it, cleansing it by the laver of water in the word of life." St. Augustine says : "The word is added to the element, and this becomes the sacrament." Augustine : "It is impossible to keep men together in one religious denomination, whether true or false, except they be united by means of visible signs or sacraments." It is necessary for salvation that humans united together in the name of true religion. Therefore, sacraments are necessary for man's salvation. There are three reasons sacraments are necessary to the salvation of humans: First, it is in the nature of humans to be led by things corporal and sensible to things that are spiritual and intelligible. Second, by sinning, humans have subjected themselves to corporeal things. Therefore, it is proper that the remedy have a corporeal side, leading to the spiritual. Third, humans are prone to direct their activity towards material things. Sacraments are made necessary because humans have sinned. The main effect of the sacraments is grace, in particular those involving Virtues and Gifts. Grace perfects the soul and allow participation in the Divine Nature. Furthermore, the effects of the sacraments is justification. This is an interior effect. Romans 8,33: "God justifies." Therefore, the effects of the sacraments is justification. This is an interior effect. The power of the sacraments is from God, alone. It does not matter that the minister of the sacraments may be a sinner, or evil. Augustine : "He upon Whom you shall see the Spirit, ...that John did not know that our Lord, having the authority of baptizing, would keep it to Himself, but that the ministry would certainly pass to both good and evil men...What is a bad minister to you, wherever the Lord is good?"
The history of Catholic dogmatic theology divides into three main periods: the patristic, the medieval, the modern.
Thomas Aquinas was an Italian Dominican friar, philosopher, Catholic priest, and Doctor of the Church. An immensely influential philosopher, theologian, and jurist in the tradition of scholasticism, he is also known within the latter as the Doctor Angelicus and the Doctor Communis. The name Aquinas identifies his ancestral origins in the county of Aquino in present-day Lazio, Italy. He was the foremost classical proponent of natural theology and the father of Thomism; of which he argued that reason is found in God. 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.
Acceptance and approval of capital punishment within the Catholic Church has varied throughout time, with the Church becoming significantly more critical of the practice since the mid-20th century. In 2018, the Catechism of the Catholic Church was revised to read, "in the light of the Gospel" the death penalty is "an attack on the inviolability and dignity of the person", and it now advocates for capital punishment to be abolished worldwide.
In Christian views sin is an evil human act, which violates the rational nature of man as well as God's nature and his eternal law. According to the classical definition of St. Augustine of Hippo sin is "a word, deed, or desire in opposition to the eternal law of God."
Double-truth theory is the view that religion and philosophy, as separate sources of knowledge, might arrive at contradictory truths without detriment to either.
The Latin Church, also known as the Roman Catholic Church or the Western Church is the largest particular church sui iuris of the Catholic Church, and employs the Latin liturgical rites. It is one of 24 such churches, the 23 others forming the Eastern Catholic Churches. It is headed by the bishop of Rome, the pope – traditionally also called the patriarch of the West – with his cathedra in this role at the Archbasilica of Saint John Lateran in Rome, Italy. The Latin Church traces its history to the earliest days of Christianity through its direct leadership under the Holy See that according to Catholic tradition was founded by Peter and Paul.
The philosophy of happiness is the philosophical concern with the existence, nature, and attainment of happiness. Some philosophers believe happiness can be understood as the moral goal of life or as an aspect of chance; indeed, in most European languages the term happiness is synonymous with luck. Thus, philosophers usually explicate on happiness as either a state of mind, or a life that goes well for the person leading it. Given the pragmatic concern for the attainment of happiness, research in psychology has guided many modern day philosophers in developing their theories.
Treatise on Law is Thomas Aquinas' major work of legal philosophy. It forms questions 90–108 of the Prima Secundæ of the Summa Theologiæ, Aquinas' masterwork of Scholastic philosophical theology. Along with Aristotelianism, it forms the basis for the legal theory of Catholic canon law.
Firstly, economics in the Middle Ages worked very differently from how they operate in the modern age. The Fifth Lateran Council defined usury as "from its use, a thing which produces nothing is applied to the acquiring of gain and profit without any work, any expense or any risk",and that the modern idea of what the usury is cannot be applied to Thomasian thought.
St. Thomas asserted that usury was a violation of natural moral law. All things are created for their natural end (Aristotle). Money is not an end but a means of buying goods and services. Putting money out for the generation of more money is an evil unto itself. The formal value of money is the face value. Yet usury allows this face value to fluctuate, and hence the value of money can be diminished, thereby robbing the person who has purchased the money for use. Money stands alone as a non-vendible substance which is degraded from its natural end by selling.
Another argument used by Aquinas was that of the Roman distinction between consumable goods and non-consumable goods. Food and clothes are consumable in that once they are used, they are gone. A piece of land is non-consumable since it can produce crops for years, yet never lose its value. Money as defined by Aquinas is a consumable. To put it out for profit betrays its purpose in natural law. This is the view that prevailed for the next three centuries following St. Thomas' death.
Yet it was the one Realistic Scholastic interpretation of natural law that was completely disconnected from the economic reality of the day. The time of Aquinas was one where land feudalism was ceding prominence to money capitalism. Over the next several centuries it became clear that capitalism would provide a greater amount of goods and services than any other system.
Even in the time of Aquinas (and before), kings and popes engaged in usury. Some of the effects of Protestantism were a clarification of the views and acceptance of the practice of usury. Profit from lending became an acceptable goal. The Council of Trent (1545–1563) adopted Aquinas' view of usury, calling it a sin of equal gravity to that of homicide. This included putting money out for any return, no matter how minimal. It can be argued that this rigid stance may have encouraged the Protestant movement in larger money and trading centers.
Our views concerning capitalism, unfair labor practice, living wage, price gouging, monopolies, fair trade practices, and predatory pricing, inter alia, are remnants of the inculcation of Aquinas' interpretation of natural moral law. (See Colish p. 333–334).
The issue was never as clear as the stance Aquinas took would indicate. From Pope Gregory IX (written about 1241, when Aquinas was 16 years old): "He who loans a sum of money to one sailing or going to market, since he has assumed upon himself a risk, is not to be considered a usurer who will receive something beyond his lot. He also who gives ten solidi (a monetary unit), so that at another time just as many measures of grain, wine and oil may be paid back to him, and although these are worth more at the present time, it is probably doubtful whether at the time of payment, they will be worth more or less, for this reason, should not be considered a usurer. By reason of this doubt he is also excused, who sells clothing, grain, wine, oil, or other wares so that as a set time he receives for them more than they are worth at that time, if however, he had not intended so to sell them at the time of the contract." (See Denzinger, p. 178). In other words, if the lender of the money "assumed the risk" ("assumpsit" in Latin), along with the borrower, it was not usury.
A century earlier, in the Second Lateran Council, (Second Council of the Lateran), under the aegis of Pope Innocent II (1139) called the practice of loaning money "detestable and shameful... insatiable rapacity of money lenders, forbidden both by divine and human laws throughout the Old and New Testament, we condemn, and separate from the ecclesiastical consolation..." (Denzinger p. 148–149).
The Council of Vienne (1311–1312) under Pope Clement V declared: "If anyone shall fall into that error, so that he obstinately presumes to declare that it is not a sin to exercise usury, we decree that he must be punished as a heretic." (Denzinger p. 189). The distinction between usury and putting money out while "assuming the risk" was not mentioned. However, it could be argued that any time one assumed the risk, it was not considered usury.
There was always some confusion, and variance, in this teaching during the Middle Ages. The Fifth Lateran Council, (1515) decreed that a "reasonable degree of return" was allowable. (Denzinger p. 238). The social evil that was associated with usury was the fact that poor tenant farmers and city dwellers were often thrown into prison, or even killed if they could not repay the money they borrowed, and the interest charged. In these cases, the lenders of the money had assumed no risk. The Franciscan St. Anthony of Padua (1195–1231 AD) preached against this evil.
These events were occurring at a time when the Ecclesiastical Courts had great judicial power. There were several philosophical cross currents at play. On the one hand, the Canon Lawyers looked favorably on the products of labor, wages and profit, while holding suspect speculation, banking and finance. The Church discountenanced the fluctuations of wages and prices caused by the law of supply and demand. There was an attempt to maintain fixed standards of value. At the same time, there was a liberal and equitable view toward the old Roman idea of "contract". The Church Courts invented and refined the idea of "consideration" ; the quid pro quo in modern contract. This was something that was lacking in Roman contract. Insurance, assignability and negotiability were developments in the Church Courts. These areas were largely ignored by the Common Law, or secular law of the day, especially in England (Plucknett p. 302,304).
The Catholic Church's teaching on social doctrine has grown significantly more complicated since that time. It is beyond the scope of this article to delve into modern teaching. A summary can be found in the new Catechism of the Catholic Church, sections 2419–2463.
The question frequently arose whether the children of Jews and other heretics and non-believers should be baptized against the will of their parents. Two schools of thought were generally followed:
Therefore, even if children were being reared in error, the Church had no authority to intervene. This was the position taken by Aquinas. From Summa Theologica II-II Q. 10 Art. 12:
The question was again addressed by Aquinas in Summa Theologica III Q. 68 Art. 10:
The issue was discussed in a papal bull by Pope Benedict XIV (1747) where both schools were addressed. The pope noted that the position of Aquinas had been more widely held among theologians and canon lawyers, than that of John Duns Scotus (See Denzinger).
A primary goal of all philosophy is the proof of existence: the existence of God, the universe, and the self (see Colish, Macdonald-Cornford, Russell, Nahm, Pieper, Gilson). Although St. Thomas "five proofs" are the most referenced, they are targeted toward a Catholic audience. In Summa Contra Gentiles, Thomas provides a much lengthier and detailed proof that does not rely on divine revelation. God's existence is established based on the proposition that man's reason is capable of apprehending a cause from its effects. After analyzing motion, it becomes apparent that the first mover must be unmoved, without cause, and uncreated. From this, it then follows that the unmoved mover must be without change, and, therefore, must be eternal. The understanding that goodness and being are interchangeable leads to the realization that God is goodness. God is also found to be intelligent because he is not composed of matter nor is the form of any body. Since God is the first cause, His effects can be observed by the diversity found in creation, and the study of this is the study of Divine Providence. After building a foundation of proofs based upon natural reasoning, Aquinas then demonstrates that the Catholic Faith cannot be disproved and goes on to defend various positions against the Incarnation, the sacraments, and the Resurrection. This line of thought is also followed in the Summa Theologica and the Compendium of Theology.
A basic question of Greek Philosophy: Can an organized hierarchy (as is seen in nature) exist in the absence of an intelligence? In the atheistic view, the answer is "yes". If one answers "no", then there is a necessity of an intelligent God. The Greeks called this ultimate intelligence the "gnos" or "nous" (Nahm pp. 1–28). However, the intimate nature of this intelligence cannot be delineated by human contemplation. Many philosophers concluded that the Universe itself, was the God (Gilson). It was basically indifferent the needs of the human. This is very different from the Judeo-Christian concept of an intimate and loving God, aware of all.
Some Greek philosophers such as Zeno of Citium, Chrysippus, Plotinus, Xenophanes, 29-83; Russell pp. 453–463). This God had to be intelligent.Thales of Miletus, Heraclitus, Parmenides, Socrates, Plato and Aristotle came to the conclusion that there had to be a God. Their conclusions were based on various physical observations: there could be no infinity of actions, therefore, there must be an unmoving mover, which moves without moving. This is the prime mover. There has to be a beginning and an end, otherwise, everything would have happened long ago and not now. This is also seen in Jewish philosophy (which may be based on Greek philosophy). There must be an ultimate smallness, of which there can be nothing smaller: the atomus (Leucippus, Democritus). This was in response to the Paradoxes of Zeno: there could be no motion, since every moving body would have to pass through half the distance, then one-quarter the distance, etc. A body could not pass through an infinite number of points. This led to the conclusion that all nature was united: the doctrine of the "One". Therefore, the human mind could reasonably conclude that there was a single God, and that this God existed (For an overview see Gilson p.
When Moses wished to know the name of God in order to reveal it to the Jewish people, he asked God directly. Exodus 3, 13-14: "'Lo! I go to the children of Israel, and I shall say to them: the God of your fathers sent me to you. If they ask me His name what shall I say to them?' God replied: 'I Am Who Am.' Then He added, 'Thus will you reply to the children of Israel: He Who Is sends me to you.'" Therefore, the proper name of God is "I Am" or "Who Is". This was a remarkable exposition on several levels. First, the idea that the great, unapproachable God of the Hebrews would provide His name was exceptional. Recall that in these ancient cultures, to know the name of a person was to possess them, or a part of them, in some way. Also, the name is unusual. What did this mean? (Gilson) The only means available to the early Christians for evaluating philosophy was provided by the Greeks. Largely, this was within the Stoic school, which had been re-invigorated by the Persians whom Alexander the Great had brought back to Greece. These in turn, influenced the Roman Stoic Schools which affected both pagan and Christian thought (Colish pp. 9, 12,21, 179-180, 300-301; Russell pp. 252–270). Christianity has been described as a religion without a need for a philosophic basis. The Stoics gave it one (Gilson, p. 84).
St. Augustine was convinced that the God of Exodus was Plato's being. He speculated that Plato must have known of Exodus. "But what makes me almost subscribe to the idea that Plato was not completely ignorant of the Old Testament is that when the Angel conveys the words of God to the holy man Moses, who asks the name of the one who is sending him to proceed to the deliverance of the Hebrew people, the reply is: 'I Am Who Am', and you are to say to the children of Israel: 'it is He Who is Who has sent me to you.' It was as if, in comparison with him who truly is because he is immovable, he who has been made movable did not exist. Now Plato was intensely convinced of this and he took great care to say so." (Augustine De Civ. Dei 8:11, PL 41,236). The Being in Exodus was the same immovable entity of Plato, according to Augustine. he called the immovable being of Plato, "The first and highest being is that which is entirely immovable, and which can say by full right: 'I Am Who Am'; and you will tell them, 'He Who Is has sent me to you.'" (St. Augustine, De doctrina christiana, I, 32,5; PL 34, 32).
St. Augustine had a very deep sense of the difficulty of the problem presented by this tract. He asked the question "I Am" what? From John 8, 24: "If you do not believe that I Am, you will die in your sins." But Augustine asked, "si non credideritis quia ego sum?" (I Am What?) There was nothing added. Augustine found this embarrassing. "We were waiting for Him to say what He was, and He says nothing." Augustine: "If you do not believe that I Am the Christ; if you do not believe that I Am the Son of God; if you do not believe that I Am the Word of the Father; if you do not believe that I Am the author of the world; if you do not believe that I Am the former and the reformer of man, his creator and recreator, He Who made him and remade him; if you do not believe that I Am that, you will die in your sins. This I Am, He says He Is, is embarrassing. Even if Moses could understand this, how could the people to whom he was being sent understand it? In point of fact, he did add: 'I Am the God of Abraham, and the God of Isaac, and the God of Jacob (Exodus 3, 13-15)(Augustine on the Gospel of St. John) (Gilson, p. 85)
This is the source of the doctrine of divine essentiality or essentialist theology of Augustine which would influence Richard of St. Victor, Alexander of Hales and St. Bonaventure. By this method, the essence of God is defined by what God is, and also by describing what God is not (negative theology). St. Thomas took the text of Exodus beyond the explanation of essential theology. He bridged the gap of understanding between the being of essence and the being of existence. In Summa Theologica, the way is prepared with the proofs for the existence of God. All that remained was to recognize the God of Exodus as having the nature of "Him Who is the supreme act of being". God is simple, there is no composition in God. In this regard, Aquinas relied on Boethius who in turn followed the path of Platonism, something Aquinas usually avoided. The conclusion was that the meaning of "I Am Who Am" is not an enigma to be answered, but the statement of the essence of God. This is the discovery of Aquinas: the essence of God is not described by negative analogy, but the "essence of God is to exist". This is the basis of "existential theology" and leads to what Gilson calls the first and only existential philosophy. In Latin, this is called "Haec Sublimis Veritas", "the sublime truth". The revealed essence of God is to exist, or in the words of Aquinas, I am the pure Act of Being. This has been described as the key to understanding Thomism. Thomism has been described (in terms of a philosophic movement), as either the emptiest, or the fullest of philosophies (for a full discussion, see Gilson, pp. 84–95).