Variant translation: Now slavery has a certain likeness to death, hence it is also called civil death. For life is most evident in a thing's moving itself, while what can only be moved by another, seems to be as if dead. But it is manifest that a slave is not moved by himself, but only at his master's command. <br class="br"> Chapter 14 https://www.pathsoflove.com/aquinas/perfection-of-the-spiritual-life.html#chapter14 <br class="br"> On The Perfection of the Spiritual Life https://www.pathsoflove.com/aquinas/perfection-of-the-spiritual-life.html (1269-1270) <br class="br">Original: (la) Vita enim in hoc maxime manifestatur quod aliquid movet se ipsum; quod autem non potest moveri nisi ab alio, quasi mortuum esse videtur.

“The Jews should not be allowed to keep what they have obtained from others by usury; it were best that they were compelled to worked so that they could earn their living instead of doing nothing but becoming avaricious.”

Thomas Aquinas

On the Governance of the Jews.

“Nothing is in the intellect that was not first in the senses.”

Thomas Aquinas

q. 2, art. 3, arg. 19
This is known as the Peripatetic axiom.
De veritate (c. 1256–1259)

“Grace does not destroy nature but perfects it.”

Thomas Aquinas book Summa Theologica

I, q. 1, art. 8, ad 2
Summa Theologica (1265–1274)

“Now, as the Word of God is the Son of God, so the love of God is the Holy Spirit.”

Thomas Aquinas

Sermon on the Apostles' Creed (c. 1273), Art. 8

“No evil can be excused because it is done with a good intention.”

Thomas Aquinas

Original: (la) Nullum malum bona intentione factum excusatur.
Variant: Variant translation: An evil action cannot be justified by reference to a good intention.
Source: On the Ten Commandments (c. 1273)

“The law of nature […] is nothing other than the light of the intellect planted in us by God, by which we know what should be done and what should be avoided. God gave us this light or law in creation.”

Thomas Aquinas

Original: (la) Lex naturae […] nihil aliud est nisi lumen intellectis insitum nobis a Deo, per quod cognoscimus quid agendum et quid vitandum. Hoc lumen et hanc legem dedit Deus homini in creatione.
Source: On the Ten Commandments (c. 1273) Art. 1

“Prostitution in towns is like the sewer in a palace; take away the sewers and the palace becomes an impure and stinking place.”

Thomas Aquinas

Misattributed
Source: This quote, frequently attributed to Aquinas, is actually a paraphrase of a passage (itself an elaborate paraphrase of Augustine) by Ptolemy of Lucca in his continuation of an unfinished work by Aquinas. The passage from Ptolemy reads: "Thus, Augustine says that a whore acts in the world as the bilge in a ship or the sewer in a palace: 'Remove the sewer, and you will fill the palace with a stench.' Similarly, concerning the bilge, he says: 'Take away whores from the world, and you will fill it with sodomy.'" (Ptolemy of Lucca and Thomas Aquinas, On the Government of Rulers, trans. James M. Blythe. Philadelphia: University of Pennsylvania Press, 1997, 4. 14. 6). What Augustine actually wrote (in De ordine, 2. 4. 12) was simply: "Remove prostitutes from human affairs and you will unsettle everything on account of lusts." Only Book 1 and the first four chapters of Book 2 of On the Government of Rulers (De Regimine Principum) are by Aquinas. The rest of the work was written by Ptolemy. (It even mentions the coronation of Albert I of Hapsburg, an event that occurred in 1298, twenty-four years after Aquinas's death.) The quote comes from Book 4, which was definitely not written by Aquinas.

“There is no order between created being and non-being, but there is between created and uncreated being.”

Thomas Aquinas

Source: De potentia (c. 1265–1266) q. 7, art. 9, ad 8

“Man reaches the highest point of his knowledge about God when he knows that he knows him not, inasmuch as he knows that that which is God transcends whatsoever he conceives of him.”

Thomas Aquinas

Source: De potentia (c. 1265–1266) q. 7, art. 5, ad 14

“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.”

Thomas Aquinas book Summa Theologica

Source: Summa Theologica (1265–1274) II–II, q. 11, art. 3 co

“Perfect happiness can consist in nothing else than the vision of the Divine Essence.”

Thomas Aquinas book Summa Theologica

Source: Summa Theologica (1265–1274), I–II, q. 3, art. 8 co