For a man who has a bad will can use ill even the good he has, as when a grammarian of his own will speaks incorrectly.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic good
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/17611/pg17611-images.html

Context

“And this because, since good absolutely considered consists in act, and not in potentiality, and the ultimate act is operation, or the use of something possessed, it follows that the absolute good of man consists in good operation, or the good use of something possessed. Now we use all things by the act of the will. Hence from a good will, which makes a man use well what he has, man is called good, and from a bad will he is called bad. For a man who has a bad will can use ill even the good he has, as when a grammarian of his own will speaks incorrectly. Therefore, because the fault itself consists in the disordered act of the will, and the pain consists in the privation of something used by the will, fault has more of evil in it than pain has. The second reason can be taken from the fact that God is the author of the evil of pain, but not of the evil of fault.” source