For a man's act is made good through attaining the rule of reason, which is the rule whereby human acts are regulated.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic reason rules
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

“that "the entire structure of good works is built on four virtues," viz. temperance, prudence, fortitude and justice. I answer that, A human virtue is one "which renders a human act and man himself good" [*Ethic. ii, 6] , and this can be applied to justice. For a man's act is made good through attaining the rule of reason, which is the rule whereby human acts are regulated. Hence, since justice regulates human operations, it is evident that it renders man's operations good, and, as Tully declares (De Officiis i, 7) , good men are so called chiefly from their justice, wherefore, as he says again” source