But grace is nobler than the nature of the soul, since we can do many things by grace, to which nature is not equal, as stated above (Q. 109, AA. 1, 2, 3). Therefore grace is not a quality.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic quality state
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

“For no quality acts on its subject, since the action of a quality is not without the action of its subject, and thus the subject would necessarily act upon itself. But grace acts upon the soul, by justifying it. Therefore grace is not a quality.
Obj. 2: Furthermore, substance is nobler than quality. But grace is nobler than the nature of the soul, since we can do many things by grace, to which nature is not equal, as stated above (Q. 109, AA. 1, 2, 3). Therefore grace is not a quality. Obj. 3: Furthermore, no quality remains after it has ceased to be in its subject. But grace remains; since it is not corrupted, for thus it would be reduced to nothing, since it was created from nothing; hence it is called a "new creature" (Gal.” source