By sinning man departs from the order of reason, and consequently falls away from the dignity of his manhood, in so far as he is naturally free, and exists for himself, and he falls into the slavish state of the beasts, by being disposed of according as he is useful to others.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic sin dignity
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“This also does human justice imitate according to its powers; for it puts to death those who are dangerous to others, while it allows time for repentance to those who sin without grievously harming others. Reply Obj. 3: By sinning man departs from the order of reason, and consequently falls away from the dignity of his manhood, in so far as he is naturally free, and exists for himself, and he falls into the slavish state of the beasts, by being disposed of according as he is useful to others. This is expressed in Ps. 48:21: "Man, when he was in honor, did not understand; he hath been compared to senseless beasts, and made like to them," and Prov. 11:29: "The fool shall serve the wise." Hence, although it be evil in itself to kill a man so long as he preserve his dignity, yet it may be good to kill a man who has sinned, even as it is to kill a beast.” source