Thomas Aquinas viewed theology, "the sacred
doctrine", as a science, However, Thomas also makes a distinction between "demonstrations" of sacred doctrines and the "persuasiveness" of those doctrines. The former is akin to something like "certainty", whereas the latter is more probabilistic in nature. For example, Thomas argues that we would expect God to become incarnate, and we would expect a resurrected Christ to
not stay on Earth.
Reconciling faith and reason According to Thomas, faith and reason complement rather than
contradict each other, each giving different views of the same truth. A discrepancy between faith and reason arises from a shortcoming of either natural science or scriptural interpretation. Faith can reveal a divine mystery that eludes scientific observation. On the other hand, science can suggest where fallible humans misinterpret a scriptural metaphor as a literal statement of fact.
God Augustine of Hippo's reflection on divine essentiality, or
essentialist theology, would influence
Richard of Saint Victor,
Alexander of Hales and Bonaventure. By this method, the
essence of God is defined by what God is, and also by describing what God is not (
negative theology). 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, Thomas relied on
Boethius who in turn followed the path of
Platonism, something Thomas usually avoided. The conclusion was that the meaning of "I Am Who I Am" is not an enigma to be answered, but a statement of the essence of God. This is the discovery of Thomas: 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 , "the sublime truth". The revealed essence of God is to exist, or in the words of Thomas, "I am the pure Act of Being". This has been described as the key to understanding
Thomism. Thomism has been described (as a philosophical movement), as either the emptiest or the fullest of philosophies. He also maintains that God creates , from nothing, that is he does not make use of any preexisting matter. On the other hand, Thomas thought that the fact that the world started to exist by God's creation and is not eternal is only known to us by faith; it cannot be proved by natural reason. Like Aristotle, Thomas posited that life could form from non-living material or plant life: 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:
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. This then, we call God. • 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. This we call God. Thomas was receptive to and influenced by
Avicenna's
Proof of the Truthful. Concerning the nature of God, Thomas, like Avicenna felt the best approach, commonly called the
via negativa, was 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
Actus Essendi 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's words, "in itself the proposition 'God exists' is
necessarily true, for in it subject and predicate are the same."
Nature of sin Following 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's 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 evil Thomas Aquinas's thought on evil draws on an Augustinian inheritance that he systematises through the sixteen
Quaestiones disputatae de malo (Paris, 1269–1272) and the corresponding articles of the
Summa Theologiae.
Non-substantiality of evil Thomas takes up and rigorously formulates the Augustinian thesis: evil is neither a being nor a principle, but a
privation (
privatio): the absence of a good that ought to be present. It has neither ontological consistency nor a nature of its own. Healing offers a demonstration of this: diseases disappear without being transported elsewhere, which proves that they were not substances but deficiencies of a substance, the healthy body. In the same way, the vices of the soul vanish when it recovers its natural health. From this follows the convertibility of Being and Goodness (
bonum et ens convertuntur): every being, insofar as it exists, is good; evil can therefore signify only an absence of good, a damaging privation. It is "neither an existent nor a good": it is
other. What is sought in wrongdoing is not evil itself but the pleasure or power one believes to find there: an apparent good.
Malum poenae and malum culpae The fundamental distinction of the
De malo is that between: •
evil of punishment (
malum poenae): evil that is suffered — physical or psychological pain — which affects the creature from without; •
evil of fault (
malum culpae): evil that is caused — sin — which engages freedom and for which responsibility falls upon the agent alone. It is this second distinction that allows Thomas to exonerate divine responsibility for the production of moral evil. As
Jean-Yves Lacoste notes, Thomas holds that God "judged it better to draw good from evil than to allow no evil to exist", and that in order to clear God of responsibility for the
malum culpae, "man will be granted the privilege of being the first cause".
Evil and the perfection of the universe Thomas justifies the presence of evil in creation by the necessary
diversity of degrees of being that constitutes the perfection of the universe: the latter requires beings capable of deficiency so that every degree of being may be represented. This justification is, however, strictly
accidental: evil contributes to the universal order only by reason of the good conjoined to it, not in itself. Without this qualification, a relative positivity of evil would be conceded, which Thomas refuses.
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's five proofs for the existence of God take some of Aristotle's assertions concerning the 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 , 1650 In the
Summa Theologiae, 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 favour 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 the 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 of Laodicea's views, Thomas held that Christ had a truly human (rational)
soul, as well. This produced a duality of nature 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
Mani and
Valentinus. With respect to
Paul the Apostle'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, Augustine of Hippo, as well as the assertions of Scripture, Thomas 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." Echoing
Athanasius of Alexandria, he said that "The only begotten Son of God... assumed our nature, so that he, made man, might make men gods."
Goal of human life Thomas Aquinas 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 towards the 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) which 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. Heresy was a capital offence against the secular law of most European countries of the 13th century. 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 offences; Thomas's point seems to be that the gravity of this offence, which touches not only the material goods but also the spiritual goods of others, is at least the same as forgery. Thomas's 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 Jews, Thomas argues for toleration of both their persons and their religious rites.
Forced baptism of children of Jews and heretics The position taken by Thomas was that if children were being reared in error, the Church had no authority to intervene. From
Summa Theologiae II-II Q. 10 Art. 12: : Injustice should be done to no man. Now it would be an injustice to Jews if their children were to be baptized against their will, since they would lose the rights of parental authority over their children as soon as these were Christians. Therefore, these should not be baptized against their parent's will. The custom of the Church has been given very great authority and ought to be jealously observed in all things, since the very doctrine of Catholic Doctors derives its authority from the Church. Hence we ought to abide by the authority of the Church rather than that of an Augustine or a Jerome or any doctor whatever. Now it was never the custom of the Church to baptize the children of Jews against the will of their parents. There are two reasons for this custom. One is on account of the danger to faith. For children baptized before coming into the use of reason, might easily be persuaded by their parents to renounce what they had unknowingly embraced; and this would be detrimental to the faith. The other reason is that it is against natural justice. For a child is by nature part of its father: at first, it is not distinct from its parents as to its body, so long as it is enfolded within the mother's womb and later on after birth, and before it has the use of
free will, it is enfolded in the care of its parents, like a spiritual womb. So long as a man does not have the use of reason, he is no different from an irrational animal. Hence, it would be contrary to natural justice, if a child, before coming to the use of reason, were to be taken away from its parent's custody, or anything done against its parent's wish. The question was again addressed by Thomas in
Summa Theologiae III Q. 68 Art. 10: : It is written in the Decretals (Dist. xiv), quoting the
Council of Toledo: In regard to the Jews the holy synod commands that henceforth none of them be forced to believe; for such are not to be saved against their will, but willingly, that their righteousness may be without flaw. Children of non-believers either have the use of reason or they have not. If they have, then they already begin to control their own actions, in things that are of Divine or natural law. And therefore, of their own accord, and against the will of their parents, they can receive Baptism, just as they can contract in marriage. Consequently, such can be lawfully advised and persuaded to be baptized. If, however, they have not yet the use of free-will, according to the natural law they are under the care of their parents as long as they cannot look after themselves. For which reason we say that even the children of the ancients were saved through the faith of their parents. 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 Duns Scotus.
Magic and its practitioners Regarding magic, Thomas wrote that: • only God can perform miracles, create and transform. • angels and demons ("spiritual substances") may do wonderful things, but they are not miracles and merely use natural things as instruments. • any efficacy of magicians does not come from the power of particular words, or celestial bodies, or special figures, or sympathetic magic, but by bidding (ibid., 105) • "demons" are intellective substances which were created good and have chosen to be bad, it is these who are bid. • if there is some transformation that could not occur in nature it is either the demon working on human imagination or arranging a fake. A mention of witchcraft appears in the
Summa Theologiae and concludes that the church does not treat temporary or permanent impotence attributed to a spell any differently to that of natural causes, as far as an impediment to marriage. Under the
canon Episcopi, church doctrine held that witchcraft was not possible and any practitioners of sorcery were deluded and their acts an illusion. Thomas Aquinas was cited in a new doctrine that included the belief in witches. This was a departure from the teachings of his master Albertus Magnus whose doctrine was based in the
Episcopi. "To what extent Dominican inquisitors such as Heinrich Kramer really found support in Thomas is irrelevant in this context, thus associating Thomas's name with the whole aspect of witchcraft and the persecution of witches." The famous 15th-century witch-hunter's manual, the
Malleus Maleficarum, also written by a member of the Dominican Order, begins by quoting Thomas Aquinas refuting the
Episcopi and goes on to cite Thomas Aquinas over a hundred times. Promoters of the witch hunts that followed often quoted Thomas more than any other source. ==Philosophy==