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Summa Theologica

Aquinas began it as an orderly textbook for beginners, built every question as a staged debate, and abandoned it unfinished, calling all he had written straw.

by Thomas Aquinas8,795 passages held

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Original title
Summa Theologiae
First published
(aged 40)
Original language
Latin

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Overview

Around 1265, Thomas Aquinas set out to fix a teaching problem. The theology taught to beginners, he complained in the preface, was a clutter of disputed questions in no useful order, repeating itself and following the accidents of debate rather than the shape of the subject; he would write a text ordered as the matter itself was ordered, for students just starting out. What he produced ran to thousands of dense articles and became, against its stated purpose, one of the most demanding works in Western thought. Its architecture is the thing to grasp first. Three Parts move from God, through the human person and the whole field of moral action — the middle Part is so large it splits in two — to Christ and the sacraments; and every question breaks into Articles built the same way, each staged as a small disputation: objections first, then a terse sed contra on the other side, then Aquinas's own reasoned reply, then answers to each opening objection in turn. He never finished it. On 6 December 1273, after something happened to him during Mass that he would not describe, he stopped writing, telling a companion that everything he had done now seemed to him like straw; he died three months later, and pupils assembled the missing final section from his earlier work. Some of his positions were caught in the sweeping Paris condemnations of 1277, three years after his death. He was canonised in 1323, and in 1879 Leo XIII made his method the standard of Catholic theology — the beginners' textbook installed as the discipline's spine.

Key concepts

How is the Summa Theologica structured?

In three Parts moving from God, through the human person and the whole field of moral action, to Christ and the sacraments; the middle Part is so large it splits in two. Every question breaks into Articles built the same way: objections first, then a brief sed contra on the other side, then Aquinas's reasoned reply, then answers to each objection in turn. Aquinas designed it as an orderly textbook for beginners.

What are the Five Ways?

Five arguments in the First Part for God's existence, reasoning from features of the world to their ultimate source: from motion to a first mover, from causation to a first cause, from contingency to a necessary being, from degrees of perfection to a maximum, and from the order of nature to a governing intelligence. Each concludes to what Aquinas identifies as God. They are proofs from reason, not from scripture.

What is Aquinas's natural law?

Natural law is the rational creature's participation in the eternal law by which God orders all things. Because humans can grasp the ends their nature is directed toward, they can know its basic precepts, chiefly to do good and avoid evil, by reason alone, without revelation. Aquinas ranks it within a fourfold order of law, eternal, natural, human and divine, and makes it the moral ground shared by all people.

What is the sed contra in an Article?

The turning point of each Article. After the opening objections argue one side, the sed contra, meaning on the contrary, gives a short authority or argument for the opposing view, usually a line from scripture, Aristotle or a Father. It swings the question toward the answer Aquinas will defend in the main reply, or respondeo, which follows. It is the hinge of the disputational form.

Why did Aquinas leave the Summa unfinished?

On 6 December 1273, after something happened to him during Mass that he would not describe, he stopped writing, telling a companion that all he had done now seemed to him like straw. He died three months later, and pupils assembled the missing final section on the sacraments from his earlier work. The book that became medieval theology's spine was thus completed by other hands.

Themes of the book

What this book returns to, gathered into themes and ordered by how much of the text each one occupies.

Faith and reason, argued as one

Can revealed doctrine be reasoned about like anything else, objections raised and answered? Aquinas builds every question as a staged debate, treating theology as a science with method.

Aquinas set out to fix a teaching problem: theology for beginners was a clutter of disputes in no useful order. His remedy was an architecture. Each Article stages a small disputation, objections first, then a terse sed contra, then his own reasoned reply, then answers to each objection in turn, so a conclusion is earned against its strongest challengers. Reason and faith do not compete: some truths reason can reach, some only revelation delivers, and grace perfects nature rather than cancelling it. Behind it stands his recovery of Aristotle, whose logic he turns to the service of Christian doctrine, holding that truth cannot contradict truth.

  • reason
  • epistemology
  • logic
  • faith
  • authority
  • truth

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God as the source of all being

Can reason reach God from the world alone, without appeal to scripture? The Summa opens with five ways from ordinary things to the being on which everything else depends.

The First Part treats God and creation, and its most famous pages are the five ways, arguments from motion, causation, contingency, degrees of perfection, and the order of nature to a first mover, first cause, necessary being and governing intelligence. In God alone, Aquinas argues, essence and existence coincide: God does not have being, God is being, pure act with no unrealized potential, from whom all else receives existence. Creatures form a hierarchy of being, each a limited share in that fullness. The world is shot through with purpose, every nature inclined to an end that points beyond itself to the source that set it there.

  • metaphysics
  • causality
  • ontology
  • teleology
  • perfection
  • nature
  • hierarchy

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Happiness, virtue, law and grace

What is a human life for, and what carries a person toward it? The Summa's vast middle part maps the whole field of moral action, from happiness through virtue, law and grace.

The middle Part, so large it splits in two, treats human action as movement toward an end, and that end is happiness, found finally in the vision of God. Between it and us lie the virtues, good habits that perfect intellect and will, the moral four, prudence, justice, courage, temperance, crowned by the theological three, faith, hope and charity, which grace infuses. Law he orders in a hierarchy, eternal, natural, human and divine, natural law being reason's share in God's ordering. Sin disorders the will; grace heals and elevates what nature cannot complete alone. Charity, the love of God and neighbour, is the form and root of every real virtue.

  • ethics
  • virtue
  • will
  • intellect
  • habit
  • charity
  • justice
  • law
  • grace
  • sin

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Within this work

passages held
8,795
distinct concepts
3,695
by passages held, corpus-wide
#1

What this book thinks together

The wheel takes this book’s leading concepts and shows how often they come up together. The wider the band between two, the more of its passages speak of both. Among them, most often together: “christology” and “grace”.
Concept co-occurrence, strongest first 8 concepts, joined by 28 pairings. 86 pairings reach beyond these concepts and are not drawn.
ConceptPaired conceptShared passages
christologygrace104
moral psychologysin100
charityfaith76
gracesin74
charitysin65
charityvirtue60
charitygrace56
moral psychologyvirtue54
faithgrace53
sinvirtue46
gracevirtue43
charitymoral psychology32
faithvirtue32
christologyfaith31
faithintellect22
faithsin22
christologysin21
gracemoral psychology20
christologyintellect18
intellectmoral psychology13
charityintellect12
intellectvirtue12
charitychristology11
intellectsin11
christologyvirtue9
graceintellect8
faithmoral psychology6
christologymoral psychology2

Works held

The author's work in order, this book marked in place. Your-language title first, the original beneath it where the two differ; side chips show which full texts are held.

  1. 1265 Summa Theologica (Summa Theologiae) you are here EN
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