Saint Thomas Aquinas was an Italian Catholic philosopher and theologian in the scholastic tradition, known as Doctor Angelicus, Doctor Universalis. He is the most famous classical proponent of natural theology. He gave birth to the Thomistic school of thought (Thomism), which has long been the primary philosophical and theological approach of the Catholic Church.

Sourced

• Pange, lingua, gloriosi
  Corporis mysterium
  Sanguinisque pretiosi,
  Quem in mundi pretium
  Fructus ventris generosi
  Rex effudit gentium.
  • Translation: Sing, my tongue, the Savior's glory,
    Of His Flesh the mystery sing;
    Of the Blood, all price exceeding,
    Shed by our immortal King.
  • Pange, Lingua (hymn for Vespers on the Feast of Corpus Christi), stanza 1

• Down in adoration falling,
  Lo! the sacred Host we hail;
  Lo! o'er ancient forms departing,
  Newer rites of grace prevail;
  Faith for all defects supplying,
  Where the feeble senses fail.
  • Pange, Lingua, stanza 5 (Tantum Ergo)

• Thus Angels' Bread is made
  The Bread of man today:
  The Living Bread from Heaven
  With figures doth away:
  O wondrous gift indeed!
  The poor and lowly may
  Upon their Lord and Master feed.
  • Sacris Solemniis Juncta Sint Gaudia (Matins hymn for Corpus Christi), stanza 6 (Panis Angelicus)

• O saving Victim, opening wide
  The gate of heaven to man below,
  Our foes press on from every side,
  Thine aid supply, Thy strength bestow.
  • Verbum Supernum Prodiens (hymn for Lauds on Corpus Christi), stanza 5 (O Salutaris Hostia)

• 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).
  • The Summa Theologica (1273), Whether the woman should have been made in the first production of things

• Law: an ordinance of reason for the common good, made by him who has care of the community.
  • The Summa Theologica (1273)

• Concerning perfect blessedness which consists in a vision of God.
  • The Summa Theologica (1273)

• Three things are necessary for the salvation of man: to know what he ought to believe; to know what he ought to desire; and to know what he ought to do.
  • Two Precepts of Charity (1273)

• Reason in man is rather like God in the world.
  • Opuscule II, De Regno

• 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 power.
  • Summa Theologica,Q92, art. 1, Reply Obj. 1

• If... the motion of the earth were circular, it would be violent and contrary to nature, and could not be eternal, since ... nothing violent is eternal .... It follows, therefore, that the earth is not moved with a circular motion.
  • Commentaria in libros Aristotelis de caelo et mundo

• All that I have written seems like straw to me.
  • As quoted in The Thought of Thomas Aquinas (1993), by Brian Davies, p. 9

Attributed

• Abuse does not rule out use.

• Beware the man of one book.

• Man cannot live without joy; therefore when he is deprived of true spiritual joys it is necessary that he become addicted to carnal pleasures.

• Music is the exaltation of the mind derived from things eternal, bursting forth in sound.

• One cannot use an evil action with reference to a good intention.

• Sorrow can be alleviated by good sleep, a bath and a glass of wine.

• Sure, for all our blindness; secure, for all our helplessness; strong, for all our weakness; gaily in love, for all the pressures on our hearts.

• The most hopeful people in the world are the young and the drunk. The first because they have little experience of failure, and the second because they have succeeded in drowning theirs.

• The reason, however, why the philosopher may be likened to the poet is this: both are concerned with the marvellous.

• If forgers and malefactors are put to death by the secular power, there is much more reason for excommunicating and even putting to death one convicted of heresy.
  • Summa Theologica

• A man who works with his hands is a laborer; a man who works with his hands and his mind is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

• 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.
  • Summa Theologica, Supplement, Q98, Article 4