the natural inclination to virtue, is diminished by sin.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic virtue sin
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17897/pg17897-images.html

Context

“Accordingly, the first-mentioned good of nature is neither destroyed nor diminished by sin. The third good of nature was entirely destroyed through the sin of our first parent. But the second good of nature, viz. the natural inclination to virtue, is diminished by sin. Because human acts produce an inclination to like acts, as stated above (Q. 50, A. 1) . Now from the very fact that thing becomes inclined to one of two contraries, its inclination to the other contrary must needs be diminished.” source