The soul is the substantial perfection of the body; grace is but an accidental perfection of the soul.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic perfection body
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/19950/pg19950-images.html

Context

“and hence this union is by habitual grace, inasmuch as a perfect operation proceeds from a habit. Now the union of the human nature with the Word of God is in personal being, which depends not on any habit, but on the nature itself. Reply Obj. 2: The soul is the substantial perfection of the body; grace is but an accidental perfection of the soul. Hence grace cannot ordain the soul to personal union, which is not accidental, as the soul ordains the body. Reply Obj. 3: Our word is united to our speech, by means of breathing (spiritus) , not as a formal medium, but as a moving medium.” source