Summa Theologiae

A friar who wrote for beginners

Thomas Aquinas was born about 1225 at Roccasecca, between Rome and Naples. In 1244 he joined the new Order of Preachers, the Dominicans; he studied under Albert the Great and in 1256 became a master of theology at Paris. His life is told in Thomas Aquinas.

About 1265, in Rome, he began the Summa Theologiae, a ‘summary of theology’. Its prologue says it was written for beginners, to teach the faith in the order in which it is best learned. He was deep in the third part when, in December 1273, after something he experienced at Mass, he stopped writing; he is reported to have said that all he had written seemed to him like straw. He died the following March. The Summa breaks off in the sacrament of penance, and a Supplement drawn from his early writings completed it.

The plan, and the articles held here

The first part treats God and all things as they come from him; the second, the rational creature's return to God, in general (cited I-II: happiness, human acts, virtues, law and grace) and in particular (II-II: faith, hope, charity and the other virtues); the third, Christ, who as man is our way to God, and the sacraments. Readers hear in this plan the shape of Paul's praise:

For from Him and through Him and to Him are all things. To Him be the glory forever! Amen.

Romans 11:36

Parts divide into questions and questions into articles: I.2.3 is Part I, question 2, article 3. The library holds twenty-nine articles in nine parts: the whole first question, on sacred doctrine, from I.1.1; the three on whether God exists, ending in the ‘five ways’ of I.2.3; three on God, whether he is a body (I.3.1), can be seen (I.12.1) and can be named (I.13.1); the first on the soul (I.75.1); four on our need of grace, from I-II.109.1, and one on whether we can know we have it (I-II.112.5); the first on faith (II-II.1.1); two on why God became man, from III.1.1; three on the Passion, from III.46.1; and the first on the change of the bread and wine into Christ's body and blood (III.75.1). Most open great treatises and touch the points Christians have argued over most. Left out is nearly everything else: the Trinity, creation and providence, the virtues and the treatise on law, justification and merit, Christ's person and life, baptism and the other sacraments, and the articles after III.75.1 that explain how the bread becomes Christ's body.

How to read an article

Every article takes the same five steps, the shape of the disputations of the medieval schools. Take I.2.3, "Whether God exists?" Then come the objections, which begin "It seems that": the best case Thomas can find against his own answer. The first is evil: "If, therefore, God existed, there would be no evil discoverable; but there is evil in the world. Therefore God does not exist" I.2.3.

Next comes "On the contrary", one word from the other side, usually an authority: here God's own name, "I am Who am" I.2.3. It shows which way the answer leans, but it is not the argument, nor always Thomas's whole view; in I-II.109.3 it begins, "As some maintain" I-II.109.3.

Then comes "I answer that", his own answer: "The existence of God can be proved in five ways" I.2.3, each from the world we see. Each ends at a first cause that all call God; the questions that follow must show what it is. Last come the replies, one to each objection, often granting what is true in it. To evil he answers with Augustine: "This is part of the infinite goodness of God, that He should allow evil to exist, and out of it produce good" I.2.3.

So the first rule: what follows "It seems that" is not what Thomas thinks. The objections of I.3.1 are texts of Scripture that seem to give God a body, an arm, eyes, a throne; Thomas doubts none of them, but in the replies reads them as figures, as I.1.9 taught. The second objection of I.2.1 is Anselm's argument in the Proslogion, which Thomas does not accept as proof I.2.1. To quote an objection as Thomas's own view is the commonest way to misquote him.

Read the question and the answer first, then each objection beside its reply. Watch for distinctions: a truth may be self-evident in itself but not to us I.2.1; a thing may be needed as food is for life, or "as a horse is necessary for a journey" III.1.2.

Thomas argues from authorities, Scripture first. The Apostle is Paul and the Philosopher Aristotle; Dionysius is a writer of about 500 who took the name of Paul's Athenian convert (Acts 17:34).

Thomas read the Latin Vulgate; he cites Ecclesiasticus and Wisdom, which Protestants count among the Apocrypha, and the Vulgate numbers most Psalms one lower than our Bibles: his "Ps. lii. 1" is "The fool says in his heart" (Psalm 53:1). The library's links follow our numbering.

The English is the first edition of the Fathers of the English Dominican Province, in volumes of 1911–17, with the Douay forms of names (Osee for Hosea). In it a science is ordered knowledge drawn from first principles; charity is the love God pours into the heart; a habit is a settled disposition; and in the Eucharist the species are the visible appearances.

Reason, grace and the Word made flesh

"It was necessary for man's salvation that there should be a knowledge revealed by God" I.1.1, Thomas begins, for our end surpasses reason; and even what reason can learn of God "would only be known by a few, and that after a long time, and with the admixture of many errors" I.1.1. Yet because "God’s invisible qualities ... have been clearly seen" (Romans 1:20), God's existence can be shown from his effects, and the rule of the whole book is: "Since grace does not destroy nature, but perfects it, natural reason should minister to faith" I.1.8. In the same reply the canonical Scriptures are "an incontrovertible proof" I.1.8 and the Doctors of the church only probable. Evangelical readers welcome that; Catholics add that elsewhere Thomas calls the church's teaching the infallible rule by which faith holds to Scripture.

Theology ends in seeing God. The "On the contrary" of I.12.1 is John's promise:

Beloved, we are now children of God, and what we will be has not yet been revealed. We know that when Christ appears, we will be like Him, for we will see Him as He is.

1 John 3:2

"Hence it must be absolutely granted that the Blessed see the Essence of God" I.12.1, though none comprehends him. In this life we name him from his creatures, and no name says what he is I.13.1.

On grace Thomas is Augustine's pupil. It is "the Pelagian heresy" I-II.109.4 to think we can keep God's commandments without grace. Fallen man can still build houses and plant vineyards, but he is like a sick man who "cannot be perfectly moved with the movements of one in health, unless by the help of medicine he be cured" I-II.109.2; without healing grace he cannot love God above all things. The authority is Paul: "it does not depend on man’s desire or effort, but on God’s mercy" (Romans 9:16).

Can we know that we have grace? Some do by revelation, Thomas answers; no one by certain knowledge; anyone conjecturally, by signs, "when he is conscious of delighting in God, and of despising worldly things" I-II.112.5. His text is the Vulgate's "Man knoweth not whether he be worthy of love or hatred" I-II.112.5, where the BSB reads, "Man does not know what lies ahead, whether love or hate" (Ecclesiastes 9:1). What God promises Thomas holds "most certainly by faith" I-II.112.5; what he doubts is his own state.

Here the traditions part. Trent taught that, though none should doubt God's mercy or Christ's merit, no one can know with the certainty of faith that he has obtained grace Council of Trent, Decree on Justification, ch. 9. Calvin called "pernicious" the teaching that we have "no stronger evidence of the divine favor toward us than moral conjecture" 3.2.38, for faith rests on "a free promise in Christ" 3.2.7. The Westminster Confession holds that believers may have an infallible assurance, though it can be shaken Westminster Confession, ch. 18; Wesley, that "this faith necessarily implies an assurance" II.3.

Why did God become man? Because "it belongs to the essence of goodness to communicate itself to others" III.1.1. Not the only way to save us, it was the most fitting, and Thomas gathers its gifts from Augustine and Leo: "God was made man, that man might be made God" III.1.2, as Athanasius had said (On the Incarnation 54.3).

The Passion was necessary not by compulsion but for its end: "Was it not necessary for the Christ to suffer these things and then to enter His glory?" (Luke 24:26). Parting from Anselm (Why God Became Man I.12), Thomas holds that God could have forgiven without satisfaction and "would not have acted against justice" III.46.2. God chose the cross, he says, because by it "man knows thereby how much God loves him" III.46.3, and "this came of more copious mercy than if He had forgiven sins without satisfaction" III.46.1; the Reformers would add that Christ made satisfaction by bearing our penalty (The cross and atonement). Thomas cites Paul:

and are justified freely by His grace through the redemption that is in Christ Jesus. God presented Him as an atoning sacrifice in His blood through faith, in order to demonstrate His righteousness, because in His forbearance He had passed over the sins committed beforehand.

Romans 3:24-25

On "This is My body" (Luke 22:19) Thomas holds that Christ's true body is present, known "by faith alone, which rests upon Divine authority" III.75.1, and calls the view that it is only a sign heresy. His third objection, "But Christ's is a true body, and it is in heaven" III.75.1, is close to what the Reformed would argue; he replies that the body is there "sacramentally" III.75.1, not as in a place.

Here too the traditions part. Catholics teach transubstantiation, as Trent confirmed Council of Trent, Decree on the Eucharist; the Orthodox, a true change whose manner is a mystery; Lutherans, Christ's body in, with and under the bread; the Reformed, a true feeding on Christ by the Spirit; many others, a memorial (Baptism and the Lord's Supper).

How the church has read him

The Catholic Church made Thomas a saint in 1323 and a Doctor of the Church in 1567, calls him its Common Doctor, and since Leo XIII (1879) has set him at the centre of its schools, without binding itself to his every opinion. Luther attacked scholastic theology and its trust in Aristotle, though he knew it, many scholars note, chiefly through later schoolmen such as Gabriel Biel. Calvin faulted the schoolmen for dwelling on "the bare simple assent of the understanding" 3.2.33; Thomas does define faith as assent, given "because it is revealed by God" II-II.1.1, though he holds that living faith is formed by charity. Yet Reformed teachers such as Peter Martyr Vermigli and Girolamo Zanchi used his distinctions, and the Anglican Richard Hooker drew deeply on his teaching on law.

Evangelicals today read him in different ways. Francis Schaeffer blamed him for giving nature and reason a room of their own apart from grace; readers may test the charge against his remark that sin corrupts "the desire for good" more than "the knowledge of truth" I-II.109.2. Others find an ally: apologists use the five ways (Does God exist?), and in recent decades many Reformed and evangelical theologians have returned to the classical doctrine of God he shared with the Reformers. The differences over merit, assurance and the sacraments remain.

For Thomas the light of reason and the light of grace come from one source: "the intelligible Sun, Who is God, shines within us" I-II.109.1. The psalmist sings of the same light:

For with You is the fountain of life; in Your light we see light.

Psalm 36:9