Summa Theologica

The Summa Theologiae or Summa Theologica ('Summary of Theology'), often referred to simply as the Summa, is the best-known work of Thomas Aquinas (1225–1274), a scholastic theologian and Doctor of the Church. It 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.


 * See also: Five Ways (Aquinas)

Quotes

 * It was necessary for our salvation that there be a knowledge revealed by God, besides philosophical science built up by human reason. Firstly, indeed, because the human being is directed to God, as to an end that surpasses the grasp of his reason. "The eye hath not seen, O God, besides Thee, what things Thou hast prepared for them that wait for Thee" (Isaiah 64:4). But the end must first be known by men who are to direct their thoughts and actions to the end. Hence it was necessary for the salvation of man that certain truths which exceed human reason should be made known to him by divine revelation.
 * Part I, Question 1, Article 1; tr. Fathers of the English Dominican Province (1920, New York: Benziger Bros.)


 * Grace does not destroy nature but perfects it.
 * I, q. 1, art. 8, ad 2


 * Whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover, and, consequently, no other mover; seeing that subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.
 * I, q. 2, art. 3


 * God is the most noble of beings. Now it is impossible for a body to be the most noble of beings; for a body must be either animate or inanimate; and an animate body is manifestly nobler than any inanimate body. But an animate body is not animate precisely as body; otherwise all bodies would be animate. Therefore its animation depends upon some other thing, as our body depends for its animation on the soul. Hence that by which a body becomes animated must be nobler than the body. Therefore it is impossible that God should be a body.
 * I, q. 3


 * The fire of hell is called eternal, only because it never ends. Still, there is change in the pains of the lost...Hence in hell true eternity does not exist, but rather time.
 * I, q. 10, art. 3, ad 2


 * Whether God can make the past not to have been?
 * Objection 1: It seems that God can make the past not to have been. For what is impossible in itself is much more impossible than that which is only impossible accidentally. But God can do what is impossible in itself, as to give sight to the blind, or to raise the dead. Therefore, and much more can He do what is only impossible accidentally. Now for the past not to have been is impossible accidentally: thus for Socrates not to be running is accidentally impossible, from the fact that his running is a thing of the past. Therefore God can make the past not to have been.
 * Objection 2: Further, what God could do, He can do now, since His power is not lessened. But God could have effected, before Socrates ran, that he should not run. Therefore, when he has run, God could effect that he did not run.
 * Objection 3: Further, charity is a more excellent virtue than virginity. But God can supply charity that is lost; therefore also lost virginity. Therefore He can so effect that what was corrupt should not have been corrupt. On the contrary, Jerome says (Ep. 22 ad Eustoch.): "Although God can do all things, He cannot make a thing that is corrupt not to have been corrupted." Therefore, for the same reason, He cannot effect that anything else which is past should not have been.
 * I answer that, As was said above (Q[7], A[2]), there does not fall under the scope of God's omnipotence anything that implies a contradiction. Now that the past should not have been implies a contradiction. For as it implies a contradiction to say that Socrates is sitting, and is not sitting, so does it to say that he sat, and did not sit. But to say that he did sit is to say that it happened in the past. To say that he did not sit, is to say that it did not happen. Whence, that the past should not have been, does not come under the scope of divine power. This is what Augustine means when he says (Contra Faust. xxix, 5): "Whosoever says, If God is almighty, let Him make what is done as if it were not done, does not see that this is to say: If God is almighty let Him effect that what is true, by the very fact that it is true, be false": and the Philosopher says (Ethic. vi, 2): "Of this one thing alone is God deprived---namely, to make undone the things that have been done."
 * Reply to Objection 1: Although it is impossible accidentally for the past not to have been, if one considers the past thing itself, as, for instance, the running of Socrates; nevertheless, if the past thing is considered as past, that it should not have been is impossible, not only in itself, but absolutely since it implies a contradiction. Thus, it is more impossible than the raising of the dead; in which there is nothing contradictory, because this is reckoned impossible in reference to some power, that is to say, some natural power; for such impossible things do come beneath the scope of divine power.
 * Reply to Objection 2: As God, in accordance with the perfection of the divine power, can do all things, and yet some things are not subject to His power, because they fall short of being possible; so, also, if we regard the immutability of the divine power, whatever God could do, He can do now. Some things, however, at one time were in the nature of possibility, whilst they were yet to be done, which now fall short of the nature of possibility, when they have been done. So is God said not to be able to do them, because they themselves cannot be done.
 * Reply to Objection 3: God can remove all corruption of the mind and body from a woman who has fallen; but the fact that she had been corrupt cannot be removed from her; as also is it impossible that the fact of having sinned or having lost charity thereby can be removed from the sinner.
 * I, q. 25, art. 4


 * Reason may be employed in two ways to establish a point: firstly, for the purpose of furnishing sufficient proof of some principle, as in natural science, where sufficient proof can be brought to show that the movement of the heavens is always of uniform velocity. Reason is employed in another way, not as furnishing a sufficient proof of a principle, but as confirming an already established principle, by showing the congruity of its results, as in astrology the theory of eccentrics and epicycles is considered as established, because thereby the sensible appearances of the heavenly movements can be explained; not, however, as if this proof were sufficient, forasmuch as some other theory might explain them.
 * I, q. 32, art. 1, reply obj. 2


 * Whether the Woman should have been made in the first production of things?
 * I answer that, It was necessary for woman to be made, as the Scripture says, as a "helper" to man; not, indeed, as a helpmate in other works, as some say, since man can be more efficiently helped by another man in other works; but as a helper in the work of generation. This can be made clear if we observe the mode of generation carried out in various living things. Some living things do not possess in themselves the power of generation, but are generated by some other specific agent, such as some plants and animals by the influence of the heavenly bodies, from some fitting matter and not from seed: others possess the active and passive generative power together; as we see in plants which are generated from seed; for the noblest vital function in plants is generation. Wherefore we observe that in these the active power of generation invariably accompanies the passive power. Among perfect animals the active power of generation belongs to the male sex, and the passive power to the female. And as among animals there is a vital operation nobler than generation, to which their life is principally directed; therefore the male sex is not found in continual union with the female in perfect animals, but only at the time of coition; so that we may consider that by this means the male and female are one, as in plants they are always united; although in some cases one of them preponderates, and in some the other. But man is yet further ordered to a still nobler vital action, and that is intellectual operation. Therefore there was greater reason for the distinction of these two forces in man; so that the female should be produced separately from the male; although they are carnally united for generation. Therefore directly after the formation of woman, it was said: "And they shall be two in one flesh" (Gn. 2:24).
 * I, q. 92, art. 1


 * As regards the individual nature, woman is defective and misbegotten, for the active power of the male seed tends to the production of a perfect likeness in the masculine sex; while the production of a woman comes from defect in the active force or from some material indisposition, or even from some external influence...On the other hand, as regards human nature in general, woman is not misbegotten, but is included in nature's intention as directed to the work of generation. Now the general intention of nature depends on God, Who is the universal Author of nature. Therefore, in producing nature, God formed not only the male but also the female.
 * I, q. 92, art. 1, ad 1


 * The image of God always abides in the soul, whether this image be obsolete and clouded over as to amount to almost nothing; or whether it be obscured or disfigured, as is the case with sinners; or whether it be clear and beautiful as is the case with the just.
 * I, q. 93, art. 8, ad 3


 * Not everyone who is enlightened by an angel knows that he is enlightened by him.
 * I, q. 111, art. 1, ad 3


 * Whether the angel guardian ever forsakes a man?...It would seem that the angel guardian sometimes forsakes the man whom he is appointed to guard... On the contrary, The demons are ever assailing us, according to 1 Peter 5:8: "Your adversary the devil, as a roaring lion, goeth about, seeking whom he may devour." Much more therefore do the good angels ever guard us... the guardianship of the angels is an effect of Divine providence in regard to man. Now it is evident that neither man, nor anything at all, is entirely withdrawn from the providence of God: for in as far as a thing participates being, so far is it subject to the providence that extends over all being.
 * I, q. 113, art. 6


 * Now the object of the will, i.e., of man's appetite, is the universal good...Hence it is evident that nothing can lull the human will but the universal good. This is to be found, not in any creature, but in God alone; because every creature has goodness by participation. Thus God alone can satisfy the will of a human being.
 * I–II, q. 2, art. 8


 * Perfect happiness can consist in nothing else than the vision of the Divine Essence.
 * I–II, q. 3, art. 8 co


 * To scorn the dictate of reason is to scorn the commandment of God.
 * I-II, q. 19, art. 5


 * Beauty adds to goodness a relation to the cognitive faculty: so that "good" means that which simply pleases the appetite; while the "beautiful" is something pleasant to apprehend.
 * I–II, q. 27, art. 1, 3


 * It is written (1 John 4:16): "He that abideth in charity abideth in God, and God in him." Now charity is the love of God. Therefore, for the same reason, every love makes the beloved to be in the lover, and vice versa...the beloved is said to be in the lover, inasmuch as the beloved abides in the apprehension of the lover, according to Philippians 1:7, "For that I have you in my heart": while the lover is said to be in the beloved, according to apprehension, inasmuch as the lover is not satisfied with a superficial apprehension of the beloved, but strives to gain an intimate knowledge of everything pertaining to the beloved, so as to penetrate into his very soul.
 * I-II, q. 28, art. 2


 * it is to be observed that four proximate effects may be ascribed to love: viz. melting, enjoyment, languor, and fervor. Of these the first is "melting," which is opposed to freezing. For things that are frozen, are closely bound together, so as to be hard to pierce. But it belongs to love that the appetite is fitted to receive the good which is loved, inasmuch as the object loved is in the lover...Consequently the freezing or hardening of the heart is a disposition incompatible with love: while melting denotes a softening of the heart, whereby the heart shows itself to be ready for the entrance of the beloved.
 * I-II, q. 28, art. 5


 * The third principle [way doing good to another may give pleasure] is the motive: for instance when a man is moved by one whom he loves, to do good to someone: for whatever we do or suffer for a friend is pleasant, because love is the principal cause of pleasure.
 * I-II, q. 32, art. 6


 * Thus from the four preceding articles, the definition of law may be gathered; and it is nothing else than an ordinance of reason for the common good, made by him who has care of the community, and promulgated.
 * I-II, q. 90, art. 4


 * But if man's affection be one of passion, then it is moved also in regard to other animals: for since the passion of pity is caused by the afflictions of others; and since it happens that even irrational animals are sensible to pain, it is possible for the affection of pity to arise in a man with regard to the sufferings of animals. Now it is evident that if a man practice a pitiful affection for animals, he is all the more disposed to take pity on his fellow-men: wherefore it is written (Prov. 12:10): "The just regardeth the lives of his beasts: but the bowels of the wicked are cruel." Consequently the Lord, in order to inculcate pity to the Jewish people, who were prone to cruelty, wished them to practice pity even with regard to dumb animals, and forbade them to do certain things savoring of cruelty to animals. Hence He prohibited them to "boil a kid in the milk of its dam"; and to "muzzle the ox that treadeth out the corn"; and to slay "the dam with her young."
 * I-II, q. 102, art. 6 ad. 8


 * mysterium Christi explicite credi non potest sine fide Trinitatis.
 * The mystery of the Son cannot be explicitly believed to be true without faith in the Trinity.
 * II-II, q. 2, art. 7 resp.


 * If forgers and other malefactors are forthwith condemned to death by the secular authorities, there is much more reason for heretics, as soon as they are convicted of heresy, to be not only excommunicated but even put to death.
 * II–II, q. 11, art. 3 co


 * Yet if heretics be altogether uprooted by death, this is not contrary to Our Lord's command [in Matthew 13:30], which is to be understood as referring to the case when the cockle [weeds] cannot be plucked up without plucking up the wheat, as we explained above (10, 8, ad 1), when treating of unbelievers in general.
 * II–II, q. 11, art. 3, ad. 3


 * We ought to cherish the body. Our body's substance is not from an evil principle, as the Manicheans imagine, but from God. And therefore, we ought to cherish the body by the friendship of love, by which we love God.
 * II–II, q. 25, art. 5


 * To love is to will the good of the other.
 * I-II, q. 26, art. 4


 * Man cannot live without joy. That is why one deprived of spiritual joys goes over to carnal pleasures.
 * II–II, q. 35, art. 4, ad. 2


 * Just as it is better to illuminate than merely to shine, so to pass on what one has contemplated is better than merely to contemplate.
 * II–II, q. 188, art. 6
 * Variant: Better to illuminate than merely to shine; to deliver to others contemplated truths than merely to contemplate.
 * Original Latin: Sicut enim maius est illuminare quam lucere solum, ita maius est contemplata aliis tradere quam solum contemplari.


 * To be united to God in unity of person was not fitting to human flesh, according to its natural endowments, since it was above his dignity; nevertheless, it was fitting that God, by reason of his infinite goodness, should unite it to himself for human salvation.
 * III, q. 1, art. 2, ad 2


 * Whatever was in the human nature of Christ was moved at the bidding of the divine will; yet it does not follow that in Christ there was no movement of the will proper to human nature, for the good wills of other saints are moved by God's will... For although the will cannot be inwardly moved by any creature, yet it can be moved inwardly by God.
 * III, q. 18, art. 1, ad 1


 * Baptism is the door of the spiritual life and the gateway to the sacraments.
 * III, q. 73, art. 3


 * All admit that indulgences have some value; for it would be blasphemy to say that the Church does anything in vain.
 * Supplement, q. 25, art. 1
 * Note: This Supplement to the Third Part was compiled after Aquinas's death by Regnald of Piperno, out of material from Aquinas's much earlier Commentary on the Sentences of Peter Lombard.


 * Even as in the blessed in heaven there will be most perfect charity, so in the damned there will be the most perfect hate. Wherefore as the saints will rejoice in all goods, so will the damned grieve for all goods. Consequently the sight of the happiness of the saints will give them very great pain; hence it is written (Isaiah 26:11): "Let the envious people see and be confounded, and let fire devour Thy enemies." Therefore they will wish all the good were damned.
 * Supplement, q. 98, art. 4''